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	$172.42	6.505%	$183.6359	$183.64	$183.65	$183.60
Purchase #2	$91.45	5.596%	$96.5675	$96.57	$96.55	$96.60
Purchase #3	$130.31	10.371%	$143.8245	$143.82	$143.80	$143.80
Purchase #4	$214.69	3.591%	$222.3995	$222.40	$222.40	$222.40
Purchase #5	$235.95	4.646%	$246.9122	$246.91	$246.90	$246.90
Purchase #6	$191.72	11.471%	$213.7122	$213.71	$213.70	$213.70
Purchase #7	$158.98	10.397%	$175.5092	$175.51	$175.50	$175.50
7 purchase totals =	$1,195.52		$1,282.5610	$1,282.56	$1,282.50	$1,282.50