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	$118.45	7.647%	$127.5079	$127.51	$127.50	$127.50
Purchase #2	$238.29	10.711%	$263.8132	$263.81	$263.80	$263.80
Purchase #3	$47.35	5.833%	$50.1119	$50.11	$50.10	$50.10
Purchase #4	$215.40	10.818%	$238.702	$238.70	$238.70	$238.70
Purchase #5	$146.80	4.300%	$153.1124	$153.11	$153.10	$153.10
Purchase #6	$205.33	8.416%	$222.6106	$222.61	$222.60	$222.60
Purchase #7	$140.78	7.612%	$151.4962	$151.50	$151.50	$151.50
7 purchase totals =	$1,112.40		$1,207.3542	$1,207.35	$1,207.30	$1,207.30