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	$228.99	8.245%	$247.8702	$247.87	$247.85	$247.90
Purchase #2	$28.57	7.679%	$30.7639	$30.76	$30.75	$30.80
Purchase #3	$40.76	12.437%	$45.8293	$45.83	$45.85	$45.80
Purchase #4	$199.72	9.604%	$218.9011	$218.90	$218.90	$218.90
Purchase #5	$133.85	6.485%	$142.5302	$142.53	$142.55	$142.50
Purchase #6	$121.63	8.226%	$131.6353	$131.64	$131.65	$131.60
Purchase #7	$56.52	4.608%	$59.1244	$59.12	$59.10	$59.10
7 purchase totals =	$810.04		$876.6544	$876.65	$876.65	$876.60