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	$195.87	7.474%	$210.5093	$210.51	$210.50	$210.50
Purchase #2	$137.70	11.634%	$153.72	$153.72	$153.70	$153.70
Purchase #3	$85.87	4.294%	$89.5573	$89.56	$89.55	$89.60
Purchase #4	$152.41	8.776%	$165.7855	$165.79	$165.80	$165.80
Purchase #5	$93.49	6.371%	$99.4462	$99.45	$99.45	$99.40
Purchase #6	$169.77	5.578%	$179.2398	$179.24	$179.25	$179.20
Purchase #7	$213.44	13.833%	$242.9652	$242.97	$242.95	$243.00
7 purchase totals =	$1,048.55		$1,141.2233	$1,141.24	$1,141.20	$1,141.20