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	$47.50	9.803%	$52.1564	$52.16	$52.15	$52.20
Purchase #2	$160.69	11.497%	$179.1645	$179.16	$179.15	$179.20
Purchase #3	$87.98	3.627%	$91.171	$91.17	$91.15	$91.20
Purchase #4	$87.41	6.723%	$93.2866	$93.29	$93.30	$93.30
Purchase #5	$228.47	11.555%	$254.8697	$254.87	$254.85	$254.90
Purchase #6	$171.56	8.173%	$185.5816	$185.58	$185.60	$185.60
Purchase #7	$42.86	7.838%	$46.2194	$46.22	$46.20	$46.20
7 purchase totals =	$826.47		$902.4492	$902.45	$902.40	$902.60