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	$199.33	6.869%	$213.022	$213.02	$213.00	$213.00
Purchase #2	$214.47	8.106%	$231.8549	$231.85	$231.85	$231.90
Purchase #3	$84.73	13.822%	$96.4414	$96.44	$96.45	$96.40
Purchase #4	$83.48	11.240%	$92.8632	$92.86	$92.85	$92.90
Purchase #5	$196.56	5.242%	$206.8637	$206.86	$206.85	$206.90
Purchase #6	$78.43	12.504%	$88.2369	$88.24	$88.25	$88.20
Purchase #7	$204.31	11.805%	$228.4288	$228.43	$228.45	$228.40
7 purchase totals =	$1,061.31		$1,157.7109	$1,157.70	$1,157.70	$1,157.70