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	$168.86	12.141%	$189.3613	$189.36	$189.35	$189.40
Purchase #2	$244.25	11.152%	$271.4888	$271.49	$271.50	$271.50
Purchase #3	$98.43	12.302%	$110.5389	$110.54	$110.55	$110.50
Purchase #4	$166.48	7.126%	$178.3434	$178.34	$178.35	$178.30
Purchase #5	$214.33	12.697%	$241.5435	$241.54	$241.55	$241.50
Purchase #6	$67.59	7.311%	$72.5315	$72.53	$72.55	$72.50
Purchase #7	$224.29	13.384%	$254.309	$254.31	$254.30	$254.30
7 purchase totals =	$1,184.23		$1,318.1164	$1,318.11	$1,318.15	$1,318.00