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	$201.91	10.415%	$222.9389	$222.94	$222.95	$222.90
Purchase #2	$148.30	7.868%	$159.9682	$159.97	$159.95	$160.00
Purchase #3	$137.85	9.820%	$151.3869	$151.39	$151.40	$151.40
Purchase #4	$235.64	12.559%	$265.234	$265.23	$265.25	$265.20
Purchase #5	$234.96	5.286%	$247.38	$247.38	$247.40	$247.40
Purchase #6	$216.74	12.413%	$243.6439	$243.64	$243.65	$243.60
Purchase #7	$102.44	8.662%	$111.3134	$111.31	$111.30	$111.30
7 purchase totals =	$1,277.84		$1,401.8653	$1,401.86	$1,401.90	$1,401.80