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	$46.45	6.729%	$49.5756	$49.58	$49.60	$49.60
Purchase #2	$18.40	8.342%	$19.9349	$19.93	$19.95	$19.90
Purchase #3	$35.69	13.774%	$40.6059	$40.61	$40.60	$40.60
Purchase #4	$233.48	11.275%	$259.8049	$259.80	$259.80	$259.80
Purchase #5	$140.71	9.780%	$154.4714	$154.47	$154.45	$154.50
Purchase #6	$211.45	3.213%	$218.2439	$218.24	$218.25	$218.20
Purchase #7	$166.29	3.139%	$171.5098	$171.51	$171.50	$171.50
7 purchase totals =	$852.47		$914.1464	$914.14	$914.15	$914.10