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	$91.77	13.749%	$104.3875	$104.39	$104.40	$104.40
Purchase #2	$166.33	7.286%	$178.4488	$178.45	$178.45	$178.40
Purchase #3	$41.76	12.339%	$46.9128	$46.91	$46.90	$46.90
Purchase #4	$158.56	8.760%	$172.4499	$172.45	$172.45	$172.40
Purchase #5	$19.39	7.707%	$20.8844	$20.88	$20.90	$20.90
Purchase #6	$69.71	7.157%	$74.6991	$74.70	$74.70	$74.70
Purchase #7	$160.64	9.267%	$175.5265	$175.53	$175.55	$175.50
7 purchase totals =	$708.16		$773.3090	$773.31	$773.35	$773.20