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	$135.42	13.217%	$153.3185	$153.32	$153.30	$153.30
Purchase #2	$56.72	4.641%	$59.3524	$59.35	$59.35	$59.40
Purchase #3	$176.33	13.564%	$200.2474	$200.25	$200.25	$200.20
Purchase #4	$188.25	4.271%	$196.2902	$196.29	$196.30	$196.30
Purchase #5	$138.93	5.474%	$146.535	$146.54	$146.55	$146.50
Purchase #6	$228.54	9.842%	$251.0329	$251.03	$251.05	$251.00
Purchase #7	$179.82	4.847%	$188.5359	$188.54	$188.55	$188.50
7 purchase totals =	$1,104.01		$1,195.3123	$1,195.32	$1,195.35	$1,195.20