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	$92.90	3.219%	$95.8905	$95.89	$95.90	$95.90
Purchase #2	$92.33	12.118%	$103.5185	$103.52	$103.50	$103.50
Purchase #3	$106.91	13.650%	$121.5032	$121.50	$121.50	$121.50
Purchase #4	$107.65	3.270%	$111.1702	$111.17	$111.15	$111.20
Purchase #5	$162.84	12.698%	$183.5174	$183.52	$183.50	$183.50
Purchase #6	$56.68	8.588%	$61.5477	$61.55	$61.55	$61.50
Purchase #7	$203.31	11.582%	$226.8574	$226.86	$226.85	$226.90
7 purchase totals =	$822.62		$904.0049	$904.01	$903.95	$904.00