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	$112.53	3.363%	$116.3144	$116.31	$116.30	$116.30
Purchase #2	$108.75	9.533%	$119.1171	$119.12	$119.10	$119.10
Purchase #3	$127.32	4.854%	$133.5001	$133.50	$133.50	$133.50
Purchase #4	$105.59	12.755%	$119.058	$119.06	$119.05	$119.10
Purchase #5	$92.35	3.241%	$95.3431	$95.34	$95.35	$95.30
Purchase #6	$135.38	11.833%	$151.3995	$151.40	$151.40	$151.40
Purchase #7	$57.80	7.505%	$62.1379	$62.14	$62.15	$62.10
7 purchase totals =	$739.72		$796.8701	$796.87	$796.85	$796.80