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	$210.82	4.170%	$219.6112	$219.61	$219.60	$219.60
Purchase #2	$219.89	13.670%	$249.949	$249.95	$249.95	$249.90
Purchase #3	$83.84	6.669%	$89.4313	$89.43	$89.45	$89.40
Purchase #4	$87.25	3.330%	$90.1554	$90.16	$90.15	$90.20
Purchase #5	$139.50	5.259%	$146.8363	$146.84	$146.85	$146.80
Purchase #6	$62.48	6.507%	$66.5456	$66.55	$66.55	$66.50
Purchase #7	$226.66	10.551%	$250.5749	$250.57	$250.55	$250.60
7 purchase totals =	$1,030.44		$1,113.1037	$1,113.11	$1,113.10	$1,113.00