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	$189.71	11.768%	$212.0351	$212.04	$212.05	$212.00
Purchase #2	$153.65	9.803%	$168.7123	$168.71	$168.70	$168.70
Purchase #3	$89.81	12.492%	$101.0291	$101.03	$101.05	$101.00
Purchase #4	$89.30	3.377%	$92.3157	$92.32	$92.30	$92.30
Purchase #5	$194.71	9.306%	$212.8297	$212.83	$212.85	$212.80
Purchase #6	$101.53	9.549%	$111.2251	$111.23	$111.25	$111.20
Purchase #7	$50.68	7.136%	$54.2965	$54.30	$54.30	$54.30
7 purchase totals =	$869.39		$952.4435	$952.46	$952.50	$952.30