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	$52.95	4.865%	$55.526	$55.53	$55.55	$55.50
Purchase #2	$137.71	13.216%	$155.9098	$155.91	$155.90	$155.90
Purchase #3	$222.27	4.416%	$232.0854	$232.09	$232.10	$232.10
Purchase #4	$184.78	8.475%	$200.4401	$200.44	$200.45	$200.40
Purchase #5	$18.92	13.142%	$21.4065	$21.41	$21.40	$21.40
Purchase #6	$89.47	9.130%	$97.6386	$97.64	$97.65	$97.60
Purchase #7	$56.44	10.492%	$62.3617	$62.36	$62.35	$62.40
7 purchase totals =	$762.54		$825.3681	$825.38	$825.40	$825.30