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	$195.35	12.503%	$219.7746	$219.77	$219.75	$219.80
Purchase #2	$101.34	7.821%	$109.2658	$109.27	$109.25	$109.30
Purchase #3	$127.30	7.257%	$136.5382	$136.54	$136.55	$136.50
Purchase #4	$22.68	5.395%	$23.9036	$23.90	$23.90	$23.90
Purchase #5	$188.46	4.109%	$196.2038	$196.20	$196.20	$196.20
Purchase #6	$13.58	9.430%	$14.8606	$14.86	$14.85	$14.90
Purchase #7	$151.30	9.651%	$165.902	$165.90	$165.90	$165.90
7 purchase totals =	$800.01		$866.4486	$866.44	$866.40	$866.50