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	$138.65	4.823%	$145.3371	$145.34	$145.35	$145.30
Purchase #2	$94.63	4.499%	$98.8874	$98.89	$98.90	$98.90
Purchase #3	$108.78	13.497%	$123.462	$123.46	$123.45	$123.50
Purchase #4	$223.74	8.446%	$242.6371	$242.64	$242.65	$242.60
Purchase #5	$64.30	4.731%	$67.342	$67.34	$67.35	$67.30
Purchase #6	$147.61	13.112%	$166.9646	$166.96	$166.95	$167.00
Purchase #7	$26.50	6.132%	$28.125	$28.13	$28.15	$28.10
7 purchase totals =	$804.21		$872.7552	$872.76	$872.80	$872.70