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	$69.83	5.231%	$73.4828	$73.48	$73.50	$73.50
Purchase #2	$56.93	7.795%	$61.3677	$61.37	$61.35	$61.40
Purchase #3	$68.77	4.573%	$71.9149	$71.91	$71.90	$71.90
Purchase #4	$78.54	6.523%	$83.6632	$83.66	$83.65	$83.70
Purchase #5	$19.37	10.237%	$21.3529	$21.35	$21.35	$21.40
Purchase #6	$140.52	6.443%	$149.5737	$149.57	$149.55	$149.60
Purchase #7	$33.46	11.797%	$37.4073	$37.41	$37.40	$37.40
7 purchase totals =	$467.42		$498.7625	$498.75	$498.70	$498.90