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	$150.85	9.628%	$165.3738	$165.37	$165.35	$165.40
Purchase #2	$187.56	12.474%	$210.9562	$210.96	$210.95	$211.00
Purchase #3	$48.60	6.819%	$51.914	$51.91	$51.90	$51.90
Purchase #4	$228.97	13.277%	$259.3703	$259.37	$259.35	$259.40
Purchase #5	$123.26	9.125%	$134.5075	$134.51	$134.50	$134.50
Purchase #6	$131.38	10.155%	$144.7216	$144.72	$144.70	$144.70
Purchase #7	$32.41	11.456%	$36.1229	$36.12	$36.10	$36.10
7 purchase totals =	$903.03		$1,002.9663	$1,002.96	$1,002.85	$1,003.00