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	$83.73	11.220%	$93.1245	$93.12	$93.10	$93.10
Purchase #2	$67.67	6.797%	$72.2695	$72.27	$72.25	$72.30
Purchase #3	$81.81	3.142%	$84.3805	$84.38	$84.40	$84.40
Purchase #4	$40.48	7.684%	$43.5905	$43.59	$43.60	$43.60
Purchase #5	$26.26	6.277%	$27.9083	$27.91	$27.90	$27.90
Purchase #6	$206.92	7.527%	$222.4949	$222.49	$222.50	$222.50
Purchase #7	$166.45	8.598%	$180.7614	$180.76	$180.75	$180.80
7 purchase totals =	$673.32		$724.5296	$724.52	$724.50	$724.60