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	$168.29	11.558%	$187.741	$187.74	$187.75	$187.70
Purchase #2	$185.80	8.188%	$201.0133	$201.01	$201.00	$201.00
Purchase #3	$168.53	13.752%	$191.7062	$191.71	$191.70	$191.70
Purchase #4	$249.47	10.443%	$275.5222	$275.52	$275.50	$275.50
Purchase #5	$100.32	11.370%	$111.7264	$111.73	$111.75	$111.70
Purchase #6	$128.56	13.610%	$146.057	$146.06	$146.05	$146.10
Purchase #7	$93.31	12.547%	$105.0176	$105.02	$105.00	$105.00
7 purchase totals =	$1,094.28		$1,218.7837	$1,218.79	$1,218.75	$1,218.70