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	$31.45	5.397%	$33.1474	$33.15	$33.15	$33.10
Purchase #2	$51.36	11.713%	$57.3758	$57.38	$57.40	$57.40
Purchase #3	$59.49	3.748%	$61.7197	$61.72	$61.70	$61.70
Purchase #4	$150.29	9.580%	$164.6878	$164.69	$164.70	$164.70
Purchase #5	$119.54	7.788%	$128.8498	$128.85	$128.85	$128.80
Purchase #6	$235.87	12.358%	$265.0188	$265.02	$265.00	$265.00
Purchase #7	$144.96	4.506%	$151.4919	$151.49	$151.50	$151.50
7 purchase totals =	$792.96		$862.2912	$862.30	$862.30	$862.20