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	$200.56	4.220%	$209.0236	$209.02	$209.00	$209.00
Purchase #2	$147.73	8.229%	$159.8867	$159.89	$159.90	$159.90
Purchase #3	$238.65	7.327%	$256.1359	$256.14	$256.15	$256.10
Purchase #4	$114.43	8.588%	$124.2572	$124.26	$124.25	$124.30
Purchase #5	$95.88	4.864%	$100.5436	$100.54	$100.55	$100.50
Purchase #6	$63.72	4.328%	$66.4778	$66.48	$66.50	$66.50
Purchase #7	$112.42	10.344%	$124.0487	$124.05	$124.05	$124.00
7 purchase totals =	$973.39		$1,040.3735	$1,040.38	$1,040.40	$1,040.30