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	$99.33	13.634%	$112.8727	$112.87	$112.85	$112.90
Purchase #2	$84.39	11.178%	$93.8231	$93.82	$93.80	$93.80
Purchase #3	$125.51	4.243%	$130.8354	$130.84	$130.85	$130.80
Purchase #4	$170.61	9.670%	$187.108	$187.11	$187.10	$187.10
Purchase #5	$234.36	11.758%	$261.916	$261.92	$261.90	$261.90
Purchase #6	$184.39	3.120%	$190.143	$190.14	$190.15	$190.10
Purchase #7	$38.95	4.733%	$40.7935	$40.79	$40.80	$40.80
7 purchase totals =	$937.54		$1,017.4917	$1,017.49	$1,017.45	$1,017.40