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	$233.76	12.147%	$262.1548	$262.15	$262.15	$262.20
Purchase #2	$62.87	4.650%	$65.7935	$65.79	$65.80	$65.80
Purchase #3	$64.39	10.292%	$71.017	$71.02	$71.00	$71.00
Purchase #4	$160.73	6.690%	$171.4828	$171.48	$171.50	$171.50
Purchase #5	$111.83	6.768%	$119.3987	$119.40	$119.40	$119.40
Purchase #6	$129.56	11.476%	$144.4283	$144.43	$144.45	$144.40
Purchase #7	$31.87	5.549%	$33.6385	$33.64	$33.65	$33.60
7 purchase totals =	$795.01		$867.9136	$867.91	$867.95	$867.90