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	$208.97	6.763%	$223.1026	$223.10	$223.10	$223.10
Purchase #2	$204.96	5.163%	$215.5421	$215.54	$215.55	$215.50
Purchase #3	$197.78	12.434%	$222.372	$222.37	$222.35	$222.40
Purchase #4	$175.83	12.302%	$197.4606	$197.46	$197.45	$197.50
Purchase #5	$213.66	6.597%	$227.7552	$227.76	$227.75	$227.80
Purchase #6	$242.76	6.510%	$258.5637	$258.56	$258.55	$258.60
Purchase #7	$64.38	5.504%	$67.9235	$67.92	$67.90	$67.90
7 purchase totals =	$1,308.34		$1,412.7197	$1,412.71	$1,412.65	$1,412.80