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	$243.56	4.298%	$254.0282	$254.03	$254.05	$254.00
Purchase #2	$55.53	6.487%	$59.1322	$59.13	$59.15	$59.10
Purchase #3	$103.86	11.157%	$115.4477	$115.45	$115.45	$115.40
Purchase #4	$222.63	5.336%	$234.5095	$234.51	$234.50	$234.50
Purchase #5	$233.90	7.569%	$251.6039	$251.60	$251.60	$251.60
Purchase #6	$159.36	5.541%	$168.1901	$168.19	$168.20	$168.20
Purchase #7	$225.82	13.112%	$255.4295	$255.43	$255.45	$255.40
7 purchase totals =	$1,244.66		$1,338.3411	$1,338.34	$1,338.40	$1,338.20