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	$223.53	9.365%	$244.4636	$244.46	$244.45	$244.50
Purchase #2	$86.54	11.595%	$96.5743	$96.57	$96.55	$96.60
Purchase #3	$190.84	13.730%	$217.0423	$217.04	$217.05	$217.00
Purchase #4	$44.28	9.742%	$48.5938	$48.59	$48.60	$48.60
Purchase #5	$234.34	12.761%	$264.2441	$264.24	$264.25	$264.20
Purchase #6	$247.32	3.320%	$255.531	$255.53	$255.55	$255.50
Purchase #7	$84.66	12.595%	$95.3229	$95.32	$95.30	$95.30
7 purchase totals =	$1,111.51		$1,221.7720	$1,221.75	$1,221.75	$1,221.70