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	$118.81	7.736%	$128.0011	$128.00	$128.00	$128.00
Purchase #2	$164.97	6.513%	$175.7145	$175.71	$175.70	$175.70
Purchase #3	$119.82	6.488%	$127.5939	$127.59	$127.60	$127.60
Purchase #4	$53.73	10.493%	$59.3679	$59.37	$59.35	$59.40
Purchase #5	$124.25	7.150%	$133.1339	$133.13	$133.15	$133.10
Purchase #6	$148.52	4.436%	$155.1083	$155.11	$155.10	$155.10
Purchase #7	$18.41	8.789%	$20.0281	$20.03	$20.05	$20.00
7 purchase totals =	$748.51		$798.9477	$798.94	$798.95	$798.90