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	$142.83	5.693%	$150.9613	$150.96	$150.95	$151.00
Purchase #2	$206.29	7.805%	$222.3909	$222.39	$222.40	$222.40
Purchase #3	$213.31	5.310%	$224.6368	$224.64	$224.65	$224.60
Purchase #4	$155.51	11.189%	$172.91	$172.91	$172.90	$172.90
Purchase #5	$27.64	12.735%	$31.16	$31.16	$31.15	$31.20
Purchase #6	$65.67	10.419%	$72.5122	$72.51	$72.50	$72.50
Purchase #7	$249.60	3.432%	$258.1663	$258.17	$258.15	$258.20
7 purchase totals =	$1,060.85		$1,132.7375	$1,132.74	$1,132.70	$1,132.80