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	$142.61	7.139%	$152.7909	$152.79	$152.80	$152.80
Purchase #2	$243.38	13.331%	$275.825	$275.83	$275.85	$275.80
Purchase #3	$229.93	12.453%	$258.5632	$258.56	$258.55	$258.60
Purchase #4	$74.98	11.469%	$83.5795	$83.58	$83.60	$83.60
Purchase #5	$111.57	10.688%	$123.4946	$123.49	$123.50	$123.50
Purchase #6	$91.90	3.331%	$94.9612	$94.96	$94.95	$95.00
Purchase #7	$236.30	3.569%	$244.7335	$244.73	$244.75	$244.70
7 purchase totals =	$1,130.67		$1,233.9479	$1,233.94	$1,234.00	$1,234.00