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	$217.53	5.179%	$228.7959	$228.80	$228.80	$228.80
Purchase #2	$166.66	8.777%	$181.2877	$181.29	$181.30	$181.30
Purchase #3	$223.36	9.851%	$245.3632	$245.36	$245.35	$245.40
Purchase #4	$110.77	11.833%	$123.8774	$123.88	$123.90	$123.90
Purchase #5	$138.60	4.760%	$145.1974	$145.20	$145.20	$145.20
Purchase #6	$74.54	5.303%	$78.4929	$78.49	$78.50	$78.50
Purchase #7	$30.84	4.800%	$32.3203	$32.32	$32.30	$32.30
7 purchase totals =	$962.30		$1,035.3348	$1,035.34	$1,035.35	$1,035.40