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	$108.41	6.497%	$115.4534	$115.45	$115.45	$115.50
Purchase #2	$42.39	11.680%	$47.3412	$47.34	$47.35	$47.30
Purchase #3	$64.33	8.536%	$69.8212	$69.82	$69.80	$69.80
Purchase #4	$78.60	8.254%	$85.0876	$85.09	$85.10	$85.10
Purchase #5	$174.59	8.543%	$189.5052	$189.51	$189.50	$189.50
Purchase #6	$139.56	10.708%	$154.5041	$154.50	$154.50	$154.50
Purchase #7	$131.98	10.726%	$146.1362	$146.14	$146.15	$146.10
7 purchase totals =	$739.86		$807.8489	$807.85	$807.85	$807.80