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	$155.32	12.590%	$174.8748	$174.87	$174.85	$174.90
Purchase #2	$164.35	13.448%	$186.4518	$186.45	$186.45	$186.50
Purchase #3	$55.33	10.750%	$61.278	$61.28	$61.30	$61.30
Purchase #4	$98.46	6.744%	$105.1001	$105.10	$105.10	$105.10
Purchase #5	$39.37	11.492%	$43.8944	$43.89	$43.90	$43.90
Purchase #6	$190.90	6.477%	$203.2646	$203.26	$203.25	$203.30
Purchase #7	$211.58	12.853%	$238.7744	$238.77	$238.75	$238.80
7 purchase totals =	$915.31		$1,013.6381	$1,013.62	$1,013.60	$1,013.80