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	$86.64	7.425%	$93.073	$93.07	$93.05	$93.10
Purchase #2	$53.86	10.617%	$59.5783	$59.58	$59.60	$59.60
Purchase #3	$235.37	8.662%	$255.7577	$255.76	$255.75	$255.80
Purchase #4	$228.35	3.267%	$235.8102	$235.81	$235.80	$235.80
Purchase #5	$213.86	4.734%	$223.9841	$223.98	$224.00	$224.00
Purchase #6	$55.54	5.734%	$58.7247	$58.72	$58.70	$58.70
Purchase #7	$112.95	9.697%	$123.9028	$123.90	$123.90	$123.90
7 purchase totals =	$986.57		$1,050.8308	$1,050.82	$1,050.80	$1,050.90