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	$136.25	8.231%	$147.4647	$147.46	$147.45	$147.50
Purchase #2	$83.25	3.763%	$86.3827	$86.38	$86.40	$86.40
Purchase #3	$199.61	13.156%	$225.8707	$225.87	$225.85	$225.90
Purchase #4	$233.92	9.113%	$255.2371	$255.24	$255.25	$255.20
Purchase #5	$248.78	13.333%	$281.9498	$281.95	$281.95	$281.90
Purchase #6	$146.73	13.787%	$166.9597	$166.96	$166.95	$167.00
Purchase #7	$8.32	7.241%	$8.9225	$8.92	$8.90	$8.90
7 purchase totals =	$1,056.86		$1,172.7872	$1,172.78	$1,172.75	$1,172.80