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	$227.37	4.795%	$238.2724	$238.27	$238.25	$238.30
Purchase #2	$85.30	7.551%	$91.741	$91.74	$91.75	$91.70
Purchase #3	$97.65	7.289%	$104.7677	$104.77	$104.75	$104.80
Purchase #4	$65.60	3.219%	$67.7117	$67.71	$67.70	$67.70
Purchase #5	$116.47	11.874%	$130.2996	$130.30	$130.30	$130.30
Purchase #6	$178.75	6.509%	$190.3848	$190.38	$190.40	$190.40
Purchase #7	$106.42	10.862%	$117.9793	$117.98	$118.00	$118.00
7 purchase totals =	$877.56		$941.1565	$941.15	$941.15	$941.20