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	$92.27	12.567%	$103.8656	$103.87	$103.85	$103.90
Purchase #2	$156.79	7.872%	$169.1325	$169.13	$169.15	$169.10
Purchase #3	$207.32	13.405%	$235.1112	$235.11	$235.10	$235.10
Purchase #4	$153.63	4.427%	$160.4312	$160.43	$160.45	$160.40
Purchase #5	$211.78	13.717%	$240.8299	$240.83	$240.85	$240.80
Purchase #6	$86.81	4.493%	$90.7104	$90.71	$90.70	$90.70
Purchase #7	$175.66	11.545%	$195.9399	$195.94	$195.95	$195.90
7 purchase totals =	$1,084.26		$1,196.0207	$1,196.02	$1,196.05	$1,195.90