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	$80.46	12.381%	$90.4218	$90.42	$90.40	$90.40
Purchase #2	$193.49	13.788%	$220.1684	$220.17	$220.15	$220.20
Purchase #3	$59.77	5.496%	$63.055	$63.06	$63.05	$63.10
Purchase #4	$58.90	12.247%	$66.1135	$66.11	$66.10	$66.10
Purchase #5	$209.31	6.219%	$222.327	$222.33	$222.35	$222.30
Purchase #6	$243.60	4.870%	$255.4633	$255.46	$255.45	$255.50
Purchase #7	$227.27	3.159%	$234.4495	$234.45	$234.45	$234.40
7 purchase totals =	$1,072.80		$1,151.9985	$1,152.00	$1,151.95	$1,152.00