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	$236.30	11.123%	$262.5836	$262.58	$262.60	$262.60
Purchase #2	$81.46	12.523%	$91.6612	$91.66	$91.65	$91.70
Purchase #3	$90.34	4.193%	$94.128	$94.13	$94.15	$94.10
Purchase #4	$76.91	12.613%	$86.6107	$86.61	$86.60	$86.60
Purchase #5	$223.95	11.237%	$249.1153	$249.12	$249.10	$249.10
Purchase #6	$183.60	4.683%	$192.198	$192.20	$192.20	$192.20
Purchase #7	$162.30	6.273%	$172.4811	$172.48	$172.50	$172.50
7 purchase totals =	$1,054.86		$1,148.7779	$1,148.78	$1,148.80	$1,148.80