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	$131.77	7.874%	$142.1456	$142.15	$142.15	$142.10
Purchase #2	$149.70	5.472%	$157.8916	$157.89	$157.90	$157.90
Purchase #3	$49.67	7.831%	$53.5597	$53.56	$53.55	$53.60
Purchase #4	$202.79	12.110%	$227.3479	$227.35	$227.35	$227.30
Purchase #5	$148.66	7.314%	$159.533	$159.53	$159.55	$159.50
Purchase #6	$70.27	3.116%	$72.4596	$72.46	$72.45	$72.50
Purchase #7	$139.50	9.619%	$152.9185	$152.92	$152.90	$152.90
7 purchase totals =	$892.36		$965.8559	$965.86	$965.85	$965.80