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	$116.37	13.265%	$131.8065	$131.81	$131.80	$131.80
Purchase #2	$41.53	9.701%	$45.5588	$45.56	$45.55	$45.60
Purchase #3	$211.33	5.269%	$222.465	$222.47	$222.45	$222.50
Purchase #4	$196.94	10.870%	$218.3474	$218.35	$218.35	$218.30
Purchase #5	$250.72	11.146%	$278.6653	$278.67	$278.65	$278.70
Purchase #6	$211.27	9.666%	$231.6914	$231.69	$231.70	$231.70
Purchase #7	$43.55	10.481%	$48.1145	$48.11	$48.10	$48.10
7 purchase totals =	$1,071.71		$1,176.6489	$1,176.66	$1,176.60	$1,176.70