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	$165.85	5.202%	$174.4775	$174.48	$174.50	$174.50
Purchase #2	$218.98	7.673%	$235.7823	$235.78	$235.80	$235.80
Purchase #3	$193.73	7.635%	$208.5213	$208.52	$208.50	$208.50
Purchase #4	$92.27	10.638%	$102.0857	$102.09	$102.10	$102.10
Purchase #5	$90.41	7.317%	$97.0253	$97.03	$97.05	$97.00
Purchase #6	$209.42	13.404%	$237.4907	$237.49	$237.50	$237.50
Purchase #7	$90.40	11.385%	$100.692	$100.69	$100.70	$100.70
7 purchase totals =	$1,061.06		$1,156.0748	$1,156.08	$1,156.15	$1,156.10