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	$230.64	4.851%	$241.8283	$241.83	$241.85	$241.80
Purchase #2	$190.70	10.492%	$210.7082	$210.71	$210.70	$210.70
Purchase #3	$91.49	9.449%	$100.1349	$100.13	$100.15	$100.10
Purchase #4	$241.94	11.817%	$270.53	$270.53	$270.55	$270.50
Purchase #5	$81.52	6.579%	$86.8832	$86.88	$86.90	$86.90
Purchase #6	$94.67	8.197%	$102.4301	$102.43	$102.45	$102.40
Purchase #7	$17.48	8.355%	$18.9405	$18.94	$18.95	$18.90
7 purchase totals =	$948.44		$1,031.4552	$1,031.45	$1,031.55	$1,031.30