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	$238.61	12.267%	$267.8803	$267.88	$267.90	$267.90
Purchase #2	$82.75	8.821%	$90.0494	$90.05	$90.05	$90.00
Purchase #3	$164.69	6.317%	$175.0935	$175.09	$175.10	$175.10
Purchase #4	$106.61	4.873%	$111.8051	$111.81	$111.80	$111.80
Purchase #5	$99.48	7.716%	$107.1559	$107.16	$107.15	$107.20
Purchase #6	$232.88	7.707%	$250.8281	$250.83	$250.85	$250.80
Purchase #7	$53.64	5.185%	$56.4212	$56.42	$56.40	$56.40
7 purchase totals =	$978.66		$1,059.2335	$1,059.24	$1,059.25	$1,059.20