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	$115.25	9.208%	$125.8622	$125.86	$125.85	$125.90
Purchase #2	$99.73	6.451%	$106.1636	$106.16	$106.15	$106.20
Purchase #3	$114.55	7.589%	$123.2432	$123.24	$123.25	$123.20
Purchase #4	$173.52	12.108%	$194.5298	$194.53	$194.55	$194.50
Purchase #5	$229.64	10.842%	$254.5376	$254.54	$254.55	$254.50
Purchase #6	$45.62	10.635%	$50.4717	$50.47	$50.45	$50.50
Purchase #7	$172.42	8.111%	$186.405	$186.41	$186.40	$186.40
7 purchase totals =	$950.73		$1,041.2131	$1,041.21	$1,041.20	$1,041.20