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	$93.59	7.836%	$100.9237	$100.92	$100.90	$100.90
Purchase #2	$20.57	4.538%	$21.5035	$21.50	$21.50	$21.50
Purchase #3	$223.34	7.771%	$240.6958	$240.70	$240.70	$240.70
Purchase #4	$104.91	11.506%	$116.9809	$116.98	$117.00	$117.00
Purchase #5	$128.92	3.817%	$133.8409	$133.84	$133.85	$133.80
Purchase #6	$224.57	7.717%	$241.9001	$241.90	$241.90	$241.90
Purchase #7	$238.84	13.583%	$271.2816	$271.28	$271.30	$271.30
7 purchase totals =	$1,034.74		$1,127.1265	$1,127.12	$1,127.15	$1,127.10