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	$188.98	12.801%	$213.1713	$213.17	$213.15	$213.20
Purchase #2	$212.71	10.212%	$234.4319	$234.43	$234.45	$234.40
Purchase #3	$26.64	4.660%	$27.8814	$27.88	$27.90	$27.90
Purchase #4	$195.46	7.789%	$210.6844	$210.68	$210.70	$210.70
Purchase #5	$199.92	11.468%	$222.8468	$222.85	$222.85	$222.80
Purchase #6	$21.41	4.154%	$22.2994	$22.30	$22.30	$22.30
Purchase #7	$133.89	9.429%	$146.5145	$146.51	$146.50	$146.50
7 purchase totals =	$979.01		$1,077.8297	$1,077.82	$1,077.85	$1,077.80