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	$177.42	10.851%	$196.6718	$196.67	$196.65	$196.70
Purchase #2	$92.61	11.285%	$103.061	$103.06	$103.05	$103.10
Purchase #3	$36.81	3.835%	$38.2217	$38.22	$38.20	$38.20
Purchase #4	$37.87	9.532%	$41.4798	$41.48	$41.50	$41.50
Purchase #5	$196.79	13.794%	$223.9352	$223.94	$223.95	$223.90
Purchase #6	$38.67	6.148%	$41.0474	$41.05	$41.05	$41.00
Purchase #7	$166.72	4.843%	$174.7942	$174.79	$174.80	$174.80
7 purchase totals =	$746.89		$819.2111	$819.21	$819.20	$819.20