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	$147.25	9.406%	$161.1003	$161.10	$161.10	$161.10
Purchase #2	$81.98	12.747%	$92.43	$92.43	$92.45	$92.40
Purchase #3	$111.91	11.189%	$124.4316	$124.43	$124.45	$124.40
Purchase #4	$86.86	11.410%	$96.7707	$96.77	$96.75	$96.80
Purchase #5	$161.34	6.781%	$172.2805	$172.28	$172.30	$172.30
Purchase #6	$145.63	13.642%	$165.4968	$165.50	$165.50	$165.50
Purchase #7	$245.45	9.257%	$268.1713	$268.17	$268.15	$268.20
7 purchase totals =	$980.42		$1,080.6812	$1,080.68	$1,080.70	$1,080.70