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	$14.76	11.285%	$16.4257	$16.43	$16.45	$16.40
Purchase #2	$70.47	10.658%	$77.9807	$77.98	$78.00	$78.00
Purchase #3	$202.34	3.434%	$209.2884	$209.29	$209.30	$209.30
Purchase #4	$89.77	3.424%	$92.8437	$92.84	$92.85	$92.80
Purchase #5	$160.60	3.868%	$166.812	$166.81	$166.80	$166.80
Purchase #6	$72.47	7.771%	$78.1016	$78.10	$78.10	$78.10
Purchase #7	$219.93	5.185%	$231.3334	$231.33	$231.35	$231.30
7 purchase totals =	$830.34		$872.7855	$872.78	$872.85	$872.70