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	$150.78	4.234%	$157.164	$157.16	$157.15	$157.20
Purchase #2	$240.61	9.300%	$262.9867	$262.99	$263.00	$263.00
Purchase #3	$15.31	7.287%	$16.4256	$16.43	$16.45	$16.40
Purchase #4	$46.31	6.745%	$49.4336	$49.43	$49.45	$49.40
Purchase #5	$242.46	7.189%	$259.8904	$259.89	$259.90	$259.90
Purchase #6	$175.29	9.471%	$191.8917	$191.89	$191.90	$191.90
Purchase #7	$159.27	4.139%	$165.8622	$165.86	$165.85	$165.90
7 purchase totals =	$1,030.03		$1,103.6542	$1,103.65	$1,103.70	$1,103.70