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	$242.78	7.718%	$261.5178	$261.52	$261.50	$261.50
Purchase #2	$51.50	6.300%	$54.7445	$54.74	$54.75	$54.70
Purchase #3	$152.71	8.140%	$165.1406	$165.14	$165.15	$165.10
Purchase #4	$49.76	11.854%	$55.6586	$55.66	$55.65	$55.70
Purchase #5	$158.96	11.629%	$177.4455	$177.45	$177.45	$177.40
Purchase #6	$186.29	5.331%	$196.2211	$196.22	$196.20	$196.20
Purchase #7	$127.78	11.795%	$142.8517	$142.85	$142.85	$142.90
7 purchase totals =	$969.78		$1,053.5798	$1,053.58	$1,053.55	$1,053.50