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	$86.55	5.316%	$91.151	$91.15	$91.15	$91.20
Purchase #2	$146.72	6.473%	$156.2172	$156.22	$156.20	$156.20
Purchase #3	$225.83	10.488%	$249.5151	$249.52	$249.50	$249.50
Purchase #4	$164.48	3.140%	$169.6447	$169.64	$169.65	$169.60
Purchase #5	$31.96	10.823%	$35.419	$35.42	$35.40	$35.40
Purchase #6	$203.42	13.566%	$231.016	$231.02	$231.00	$231.00
Purchase #7	$58.85	4.370%	$61.4217	$61.42	$61.40	$61.40
7 purchase totals =	$917.81		$994.3847	$994.39	$994.30	$994.30