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	$126.27	9.243%	$137.9411	$137.94	$137.95	$137.90
Purchase #2	$172.31	4.840%	$180.6498	$180.65	$180.65	$180.60
Purchase #3	$71.52	9.244%	$78.1313	$78.13	$78.15	$78.10
Purchase #4	$231.58	8.130%	$250.4075	$250.41	$250.40	$250.40
Purchase #5	$33.73	9.589%	$36.9644	$36.96	$36.95	$37.00
Purchase #6	$149.94	7.615%	$161.3579	$161.36	$161.35	$161.40
Purchase #7	$154.38	13.653%	$175.4575	$175.46	$175.45	$175.50
7 purchase totals =	$939.73		$1,020.9095	$1,020.91	$1,020.90	$1,020.90