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	$218.34	3.240%	$225.4142	$225.41	$225.40	$225.40
Purchase #2	$125.74	11.134%	$139.7399	$139.74	$139.75	$139.70
Purchase #3	$94.82	11.208%	$105.4474	$105.45	$105.45	$105.40
Purchase #4	$188.80	4.192%	$196.7145	$196.71	$196.70	$196.70
Purchase #5	$100.78	8.206%	$109.05	$109.05	$109.05	$109.10
Purchase #6	$117.72	6.574%	$125.4589	$125.46	$125.45	$125.50
Purchase #7	$111.69	6.458%	$118.9029	$118.90	$118.90	$118.90
7 purchase totals =	$957.89		$1,020.7278	$1,020.72	$1,020.70	$1,020.70