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	$219.52	6.352%	$233.4639	$233.46	$233.45	$233.50
Purchase #2	$42.33	3.318%	$43.7345	$43.73	$43.75	$43.70
Purchase #3	$173.53	8.617%	$188.4831	$188.48	$188.50	$188.50
Purchase #4	$15.86	11.681%	$17.7126	$17.71	$17.70	$17.70
Purchase #5	$161.51	10.490%	$178.4524	$178.45	$178.45	$178.50
Purchase #6	$200.53	5.480%	$211.519	$211.52	$211.50	$211.50
Purchase #7	$59.48	8.379%	$64.4638	$64.46	$64.45	$64.50
7 purchase totals =	$872.76		$937.8293	$937.81	$937.80	$937.90