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	$149.25	11.804%	$166.8675	$166.87	$166.85	$166.90
Purchase #2	$235.41	4.334%	$245.6127	$245.61	$245.60	$245.60
Purchase #3	$59.77	5.676%	$63.1625	$63.16	$63.15	$63.20
Purchase #4	$37.35	13.218%	$42.2869	$42.29	$42.30	$42.30
Purchase #5	$88.33	3.600%	$91.5099	$91.51	$91.50	$91.50
Purchase #6	$52.79	8.581%	$57.3199	$57.32	$57.30	$57.30
Purchase #7	$131.89	12.206%	$147.9885	$147.99	$148.00	$148.00
7 purchase totals =	$754.79		$814.7479	$814.75	$814.70	$814.80