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	$63.47	3.258%	$65.5379	$65.54	$65.55	$65.50
Purchase #2	$30.47	3.608%	$31.5694	$31.57	$31.55	$31.60
Purchase #3	$65.71	9.122%	$71.7041	$71.70	$71.70	$71.70
Purchase #4	$191.89	10.629%	$212.286	$212.29	$212.30	$212.30
Purchase #5	$32.28	4.328%	$33.6771	$33.68	$33.70	$33.70
Purchase #6	$131.42	11.266%	$146.2258	$146.23	$146.25	$146.20
Purchase #7	$40.87	10.541%	$45.1781	$45.18	$45.20	$45.20
7 purchase totals =	$556.11		$606.1784	$606.19	$606.25	$606.20