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	$58.47	5.636%	$61.7654	$61.77	$61.75	$61.80
Purchase #2	$55.79	10.627%	$61.7188	$61.72	$61.70	$61.70
Purchase #3	$247.89	3.524%	$256.6256	$256.63	$256.65	$256.60
Purchase #4	$73.83	3.612%	$76.4967	$76.50	$76.50	$76.50
Purchase #5	$17.54	3.306%	$18.1199	$18.12	$18.10	$18.10
Purchase #6	$71.95	5.776%	$76.1058	$76.11	$76.10	$76.10
Purchase #7	$37.94	3.605%	$39.3077	$39.31	$39.30	$39.30
7 purchase totals =	$563.41		$590.1399	$590.16	$590.10	$590.10