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	$232.25	11.320%	$258.5407	$258.54	$258.55	$258.50
Purchase #2	$151.88	10.831%	$168.3301	$168.33	$168.35	$168.30
Purchase #3	$205.84	11.856%	$230.2444	$230.24	$230.25	$230.20
Purchase #4	$59.94	9.661%	$65.7308	$65.73	$65.75	$65.70
Purchase #5	$186.47	5.369%	$196.4816	$196.48	$196.50	$196.50
Purchase #6	$84.58	9.707%	$92.7902	$92.79	$92.80	$92.80
Purchase #7	$139.92	11.390%	$155.8569	$155.86	$155.85	$155.90
7 purchase totals =	$1,060.88		$1,167.9747	$1,167.97	$1,168.05	$1,167.90