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	$234.33	13.381%	$265.6857	$265.69	$265.70	$265.70
Purchase #2	$188.43	11.429%	$209.9657	$209.97	$209.95	$210.00
Purchase #3	$13.31	5.698%	$14.0684	$14.07	$14.05	$14.10
Purchase #4	$29.26	10.513%	$32.3361	$32.34	$32.35	$32.30
Purchase #5	$249.78	11.426%	$278.3199	$278.32	$278.30	$278.30
Purchase #6	$42.70	11.266%	$47.5106	$47.51	$47.50	$47.50
Purchase #7	$72.52	13.112%	$82.0288	$82.03	$82.05	$82.00
7 purchase totals =	$830.33		$929.9152	$929.93	$929.90	$929.90