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	$215.63	3.136%	$222.3922	$222.39	$222.40	$222.40
Purchase #2	$174.50	11.386%	$194.3686	$194.37	$194.35	$194.40
Purchase #3	$215.52	4.793%	$225.8499	$225.85	$225.85	$225.80
Purchase #4	$201.91	10.588%	$223.2882	$223.29	$223.30	$223.30
Purchase #5	$23.30	10.112%	$25.6561	$25.66	$25.65	$25.70
Purchase #6	$227.55	10.383%	$251.1765	$251.18	$251.20	$251.20
Purchase #7	$36.56	9.638%	$40.0837	$40.08	$40.10	$40.10
7 purchase totals =	$1,094.97		$1,182.8152	$1,182.82	$1,182.85	$1,182.90