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	$51.84	6.721%	$55.3242	$55.32	$55.30	$55.30
Purchase #2	$93.69	4.566%	$97.9679	$97.97	$97.95	$98.00
Purchase #3	$39.81	6.439%	$42.3734	$42.37	$42.35	$42.40
Purchase #4	$224.67	11.679%	$250.9092	$250.91	$250.90	$250.90
Purchase #5	$107.47	10.249%	$118.4846	$118.48	$118.50	$118.50
Purchase #6	$43.57	10.582%	$48.1806	$48.18	$48.20	$48.20
Purchase #7	$106.96	4.592%	$111.8716	$111.87	$111.85	$111.90
7 purchase totals =	$668.01		$725.1115	$725.10	$725.05	$725.20