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	$56.87	4.191%	$59.2534	$59.25	$59.25	$59.30
Purchase #2	$231.73	3.256%	$239.2751	$239.28	$239.30	$239.30
Purchase #3	$36.46	3.676%	$37.8003	$37.80	$37.80	$37.80
Purchase #4	$112.92	10.410%	$124.675	$124.68	$124.70	$124.70
Purchase #5	$19.75	13.208%	$22.3586	$22.36	$22.35	$22.40
Purchase #6	$20.89	3.718%	$21.6667	$21.67	$21.65	$21.70
Purchase #7	$236.59	10.256%	$260.8547	$260.85	$260.85	$260.90
7 purchase totals =	$715.21		$765.8838	$765.89	$765.90	$766.10