Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$160.27	13.694%	$182.2174	$182.22	$182.20	$182.20
Purchase #2	$123.99	3.127%	$127.8672	$127.87	$127.85	$127.90
Purchase #3	$178.53	4.132%	$185.9069	$185.91	$185.90	$185.90
Purchase #4	$135.97	11.720%	$151.9057	$151.91	$151.90	$151.90
Purchase #5	$190.75	7.696%	$205.4301	$205.43	$205.45	$205.40
Purchase #6	$136.36	13.610%	$154.9186	$154.92	$154.90	$154.90
Purchase #7	$157.49	5.168%	$165.6291	$165.63	$165.65	$165.60
7 purchase totals =	$1,083.36		$1,173.8750	$1,173.89	$1,173.85	$1,173.80