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	$70.29	3.790%	$72.954	$72.95	$72.95	$73.00
Purchase #2	$240.49	3.700%	$249.3881	$249.39	$249.40	$249.40
Purchase #3	$131.81	9.319%	$144.0934	$144.09	$144.10	$144.10
Purchase #4	$10.93	4.155%	$11.3841	$11.38	$11.40	$11.40
Purchase #5	$221.89	9.478%	$242.9207	$242.92	$242.90	$242.90
Purchase #6	$27.51	3.152%	$28.3771	$28.38	$28.40	$28.40
Purchase #7	$52.96	5.447%	$55.8447	$55.84	$55.85	$55.80
7 purchase totals =	$755.88		$804.9621	$804.95	$805.00	$805.00