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	$46.76	3.461%	$48.3784	$48.38	$48.40	$48.40
Purchase #2	$229.31	12.650%	$258.3177	$258.32	$258.30	$258.30
Purchase #3	$168.50	13.690%	$191.5677	$191.57	$191.55	$191.60
Purchase #4	$26.89	5.621%	$28.4015	$28.40	$28.40	$28.40
Purchase #5	$106.95	4.756%	$112.0365	$112.04	$112.05	$112.00
Purchase #6	$99.69	11.197%	$110.8523	$110.85	$110.85	$110.90
Purchase #7	$227.78	4.804%	$238.7226	$238.72	$238.70	$238.70
7 purchase totals =	$905.88		$988.2767	$988.28	$988.25	$988.30