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	$33.36	13.744%	$37.945	$37.95	$37.95	$37.90
Purchase #2	$211.90	7.290%	$227.3475	$227.35	$227.35	$227.30
Purchase #3	$147.60	13.790%	$167.954	$167.95	$167.95	$168.00
Purchase #4	$133.41	13.318%	$151.1775	$151.18	$151.20	$151.20
Purchase #5	$195.52	11.840%	$218.6696	$218.67	$218.65	$218.70
Purchase #6	$176.89	6.330%	$188.0871	$188.09	$188.10	$188.10
Purchase #7	$40.78	6.829%	$43.5649	$43.56	$43.55	$43.60
7 purchase totals =	$939.46		$1,034.7456	$1,034.75	$1,034.75	$1,034.80