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	$148.74	3.423%	$153.8314	$153.83	$153.85	$153.80
Purchase #2	$85.74	6.491%	$91.3054	$91.31	$91.30	$91.30
Purchase #3	$161.50	12.387%	$181.505	$181.51	$181.50	$181.50
Purchase #4	$206.76	6.216%	$219.6122	$219.61	$219.60	$219.60
Purchase #5	$13.71	11.831%	$15.332	$15.33	$15.35	$15.30
Purchase #6	$238.92	4.186%	$248.9212	$248.92	$248.90	$248.90
Purchase #7	$158.51	8.586%	$172.1197	$172.12	$172.10	$172.10
7 purchase totals =	$1,013.88		$1,082.6269	$1,082.63	$1,082.60	$1,082.50