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	$61.28	4.665%	$64.1387	$64.14	$64.15	$64.10
Purchase #2	$108.30	3.769%	$112.3818	$112.38	$112.40	$112.40
Purchase #3	$23.26	3.678%	$24.1155	$24.12	$24.10	$24.10
Purchase #4	$38.30	5.382%	$40.3613	$40.36	$40.35	$40.40
Purchase #5	$28.98	13.628%	$32.9294	$32.93	$32.95	$32.90
Purchase #6	$147.93	9.243%	$161.6032	$161.60	$161.60	$161.60
Purchase #7	$72.80	8.254%	$78.8089	$78.81	$78.80	$78.80
7 purchase totals =	$480.85		$514.3388	$514.34	$514.35	$514.30