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	$159.29	12.722%	$179.5549	$179.55	$179.55	$179.60
Purchase #2	$85.37	12.139%	$95.7331	$95.73	$95.75	$95.70
Purchase #3	$66.34	9.485%	$72.6323	$72.63	$72.65	$72.60
Purchase #4	$145.83	12.606%	$164.2133	$164.21	$164.20	$164.20
Purchase #5	$238.55	11.446%	$265.8544	$265.85	$265.85	$265.90
Purchase #6	$215.59	6.742%	$230.1251	$230.13	$230.15	$230.10
Purchase #7	$5.97	11.740%	$6.6709	$6.67	$6.65	$6.70
7 purchase totals =	$916.94		$1,014.7840	$1,014.77	$1,014.80	$1,014.80