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	$62.75	12.765%	$70.76	$70.76	$70.75	$70.80
Purchase #2	$29.83	12.417%	$33.534	$33.53	$33.55	$33.50
Purchase #3	$228.99	12.717%	$258.1107	$258.11	$258.10	$258.10
Purchase #4	$35.67	10.503%	$39.4164	$39.42	$39.40	$39.40
Purchase #5	$217.88	3.570%	$225.6583	$225.66	$225.65	$225.70
Purchase #6	$199.64	11.350%	$222.2991	$222.30	$222.30	$222.30
Purchase #7	$82.54	9.534%	$90.4094	$90.41	$90.40	$90.40
7 purchase totals =	$857.30		$940.1879	$940.19	$940.15	$940.20