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	$193.88	13.150%	$219.3752	$219.38	$219.40	$219.40
Purchase #2	$199.71	6.624%	$212.9388	$212.94	$212.95	$212.90
Purchase #3	$158.92	5.745%	$168.05	$168.05	$168.05	$168.10
Purchase #4	$220.83	4.106%	$229.8973	$229.90	$229.90	$229.90
Purchase #5	$115.61	6.603%	$123.2437	$123.24	$123.25	$123.20
Purchase #6	$82.85	10.554%	$91.594	$91.59	$91.60	$91.60
Purchase #7	$72.58	12.585%	$81.7142	$81.71	$81.70	$81.70
7 purchase totals =	$1,044.38		$1,126.8132	$1,126.81	$1,126.85	$1,126.80