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	$152.31	10.741%	$168.6696	$168.67	$168.65	$168.70
Purchase #2	$180.79	9.198%	$197.4191	$197.42	$197.40	$197.40
Purchase #3	$169.72	5.672%	$179.3465	$179.35	$179.35	$179.30
Purchase #4	$127.39	9.368%	$139.3239	$139.32	$139.30	$139.30
Purchase #5	$239.35	9.654%	$262.4568	$262.46	$262.45	$262.50
Purchase #6	$88.50	3.749%	$91.8179	$91.82	$91.80	$91.80
Purchase #7	$55.84	10.248%	$61.5625	$61.56	$61.55	$61.60
7 purchase totals =	$1,013.90		$1,100.5963	$1,100.60	$1,100.50	$1,100.60