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	$246.96	11.196%	$274.6096	$274.61	$274.60	$274.60
Purchase #2	$182.34	13.791%	$207.4865	$207.49	$207.50	$207.50
Purchase #3	$159.59	5.811%	$168.8638	$168.86	$168.85	$168.90
Purchase #4	$42.59	8.807%	$46.3409	$46.34	$46.35	$46.30
Purchase #5	$124.33	5.330%	$130.9568	$130.96	$130.95	$131.00
Purchase #6	$100.86	4.444%	$105.3422	$105.34	$105.35	$105.30
Purchase #7	$49.79	9.793%	$54.6659	$54.67	$54.65	$54.70
7 purchase totals =	$906.46		$988.2657	$988.27	$988.25	$988.30