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	$188.27	11.786%	$210.4595	$210.46	$210.45	$210.50
Purchase #2	$94.89	4.754%	$99.4011	$99.40	$99.40	$99.40
Purchase #3	$64.38	6.529%	$68.5834	$68.58	$68.60	$68.60
Purchase #4	$137.92	13.810%	$156.9668	$156.97	$156.95	$157.00
Purchase #5	$132.72	4.822%	$139.1198	$139.12	$139.10	$139.10
Purchase #6	$181.65	8.733%	$197.5135	$197.51	$197.50	$197.50
Purchase #7	$217.33	10.838%	$240.8842	$240.88	$240.90	$240.90
7 purchase totals =	$1,017.16		$1,112.9283	$1,112.92	$1,112.90	$1,113.00