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	$218.77	7.616%	$235.4315	$235.43	$235.45	$235.40
Purchase #2	$72.53	7.294%	$77.8203	$77.82	$77.80	$77.80
Purchase #3	$238.52	7.287%	$255.901	$255.90	$255.90	$255.90
Purchase #4	$101.35	3.444%	$104.8405	$104.84	$104.85	$104.80
Purchase #5	$56.39	5.372%	$59.4193	$59.42	$59.40	$59.40
Purchase #6	$226.49	9.457%	$247.9092	$247.91	$247.90	$247.90
Purchase #7	$91.60	9.244%	$100.0675	$100.07	$100.05	$100.10
7 purchase totals =	$1,005.65		$1,081.3893	$1,081.39	$1,081.35	$1,081.30