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	$191.39	10.175%	$210.8639	$210.86	$210.85	$210.90
Purchase #2	$131.45	6.597%	$140.1218	$140.12	$140.10	$140.10
Purchase #3	$118.77	6.738%	$126.7727	$126.77	$126.75	$126.80
Purchase #4	$119.64	8.570%	$129.8931	$129.89	$129.90	$129.90
Purchase #5	$139.49	3.519%	$144.3987	$144.40	$144.40	$144.40
Purchase #6	$67.76	6.679%	$72.2857	$72.29	$72.30	$72.30
Purchase #7	$44.30	13.156%	$50.1281	$50.13	$50.15	$50.10
7 purchase totals =	$812.80		$874.4640	$874.46	$874.45	$874.50