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	$154.88	12.683%	$174.5234	$174.52	$174.50	$174.50
Purchase #2	$176.49	5.111%	$185.5104	$185.51	$185.50	$185.50
Purchase #3	$93.49	5.424%	$98.5609	$98.56	$98.55	$98.60
Purchase #4	$123.48	3.575%	$127.8944	$127.89	$127.90	$127.90
Purchase #5	$65.91	8.354%	$71.4161	$71.42	$71.40	$71.40
Purchase #6	$81.85	10.552%	$90.4868	$90.49	$90.50	$90.50
Purchase #7	$238.36	6.362%	$253.5245	$253.52	$253.50	$253.50
7 purchase totals =	$934.46		$1,001.9165	$1,001.91	$1,001.85	$1,001.90