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	$90.93	3.556%	$94.1635	$94.16	$94.15	$94.20
Purchase #2	$59.80	3.390%	$61.8272	$61.83	$61.85	$61.80
Purchase #3	$69.91	6.412%	$74.3926	$74.39	$74.40	$74.40
Purchase #4	$225.45	11.827%	$252.114	$252.11	$252.10	$252.10
Purchase #5	$155.81	5.661%	$164.6304	$164.63	$164.65	$164.60
Purchase #6	$158.65	12.216%	$178.0307	$178.03	$178.05	$178.00
Purchase #7	$248.92	3.178%	$256.8307	$256.83	$256.85	$256.80
7 purchase totals =	$1,009.47		$1,081.9891	$1,081.98	$1,082.05	$1,081.90