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	$95.97	8.520%	$104.1466	$104.15	$104.15	$104.10
Purchase #2	$185.43	12.103%	$207.8726	$207.87	$207.85	$207.90
Purchase #3	$203.26	6.460%	$216.3906	$216.39	$216.40	$216.40
Purchase #4	$89.73	10.538%	$99.1857	$99.19	$99.20	$99.20
Purchase #5	$191.32	11.784%	$213.8651	$213.87	$213.85	$213.90
Purchase #6	$198.80	13.587%	$225.811	$225.81	$225.80	$225.80
Purchase #7	$96.53	3.156%	$99.5765	$99.58	$99.60	$99.60
7 purchase totals =	$1,061.04		$1,166.8481	$1,166.86	$1,166.85	$1,166.90