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	$59.38	4.122%	$61.8276	$61.83	$61.85	$61.80
Purchase #2	$9.92	9.782%	$10.8904	$10.89	$10.90	$10.90
Purchase #3	$119.67	9.369%	$130.8819	$130.88	$130.90	$130.90
Purchase #4	$199.70	10.715%	$221.0979	$221.10	$221.10	$221.10
Purchase #5	$43.53	12.524%	$48.9817	$48.98	$49.00	$49.00
Purchase #6	$19.29	4.285%	$20.1166	$20.12	$20.10	$20.10
Purchase #7	$98.55	10.734%	$109.1284	$109.13	$109.15	$109.10
7 purchase totals =	$550.04		$602.9245	$602.93	$603.00	$602.90