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	$96.61	4.288%	$100.7526	$100.75	$100.75	$100.80
Purchase #2	$189.88	5.283%	$199.9114	$199.91	$199.90	$199.90
Purchase #3	$247.72	12.693%	$279.1631	$279.16	$279.15	$279.20
Purchase #4	$213.95	12.246%	$240.1503	$240.15	$240.15	$240.20
Purchase #5	$30.45	9.544%	$33.3561	$33.36	$33.35	$33.40
Purchase #6	$182.80	7.472%	$196.4588	$196.46	$196.45	$196.50
Purchase #7	$63.59	6.764%	$67.8912	$67.89	$67.90	$67.90
7 purchase totals =	$1,025.00		$1,117.6835	$1,117.68	$1,117.65	$1,117.90