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	$57.69	7.305%	$61.9043	$61.90	$61.90	$61.90
Purchase #2	$46.95	12.837%	$52.977	$52.98	$53.00	$53.00
Purchase #3	$213.87	7.129%	$229.1168	$229.12	$229.10	$229.10
Purchase #4	$25.48	8.165%	$27.5604	$27.56	$27.55	$27.60
Purchase #5	$132.74	4.766%	$139.0664	$139.07	$139.05	$139.10
Purchase #6	$120.89	7.421%	$129.8612	$129.86	$129.85	$129.90
Purchase #7	$99.47	11.694%	$111.102	$111.10	$111.10	$111.10
7 purchase totals =	$697.09		$751.5881	$751.59	$751.55	$751.70