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	$136.82	11.299%	$152.2793	$152.28	$152.30	$152.30
Purchase #2	$129.84	7.427%	$139.4832	$139.48	$139.50	$139.50
Purchase #3	$98.76	7.553%	$106.2193	$106.22	$106.20	$106.20
Purchase #4	$145.57	9.690%	$159.6757	$159.68	$159.70	$159.70
Purchase #5	$37.36	3.355%	$38.6134	$38.61	$38.60	$38.60
Purchase #6	$191.97	4.659%	$200.9139	$200.91	$200.90	$200.90
Purchase #7	$203.45	9.583%	$222.9466	$222.95	$222.95	$222.90
7 purchase totals =	$943.77		$1,020.1314	$1,020.13	$1,020.15	$1,020.10