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	$129.66	5.187%	$136.3855	$136.39	$136.40	$136.40
Purchase #2	$147.77	12.776%	$166.6491	$166.65	$166.65	$166.60
Purchase #3	$192.38	11.768%	$215.0193	$215.02	$215.00	$215.00
Purchase #4	$106.51	4.768%	$111.5884	$111.59	$111.60	$111.60
Purchase #5	$190.29	5.312%	$200.3982	$200.40	$200.40	$200.40
Purchase #6	$122.51	11.869%	$137.0507	$137.05	$137.05	$137.10
Purchase #7	$204.53	5.540%	$215.861	$215.86	$215.85	$215.90
7 purchase totals =	$1,093.65		$1,182.9522	$1,182.96	$1,182.95	$1,183.00