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	$172.91	9.846%	$189.9347	$189.93	$189.95	$189.90
Purchase #2	$25.83	11.409%	$28.7769	$28.78	$28.80	$28.80
Purchase #3	$83.92	6.109%	$89.0467	$89.05	$89.05	$89.00
Purchase #4	$209.28	6.228%	$222.314	$222.31	$222.30	$222.30
Purchase #5	$66.54	7.365%	$71.4407	$71.44	$71.45	$71.40
Purchase #6	$159.83	12.320%	$179.5211	$179.52	$179.50	$179.50
Purchase #7	$23.98	5.542%	$25.309	$25.31	$25.30	$25.30
7 purchase totals =	$742.29		$806.3431	$806.34	$806.35	$806.20