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	$166.83	3.227%	$172.2136	$172.21	$172.20	$172.20
Purchase #2	$175.47	8.618%	$190.592	$190.59	$190.60	$190.60
Purchase #3	$51.39	6.422%	$54.6903	$54.69	$54.70	$54.70
Purchase #4	$82.64	7.131%	$88.5331	$88.53	$88.55	$88.50
Purchase #5	$226.90	7.859%	$244.7321	$244.73	$244.75	$244.70
Purchase #6	$39.47	6.632%	$42.0877	$42.09	$42.10	$42.10
Purchase #7	$75.78	7.785%	$81.6795	$81.68	$81.70	$81.70
7 purchase totals =	$818.48		$874.5283	$874.52	$874.60	$874.50