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	$240.57	3.622%	$249.2834	$249.28	$249.30	$249.30
Purchase #2	$30.73	12.177%	$34.472	$34.47	$34.45	$34.50
Purchase #3	$246.42	12.690%	$277.6907	$277.69	$277.70	$277.70
Purchase #4	$218.72	10.127%	$240.8698	$240.87	$240.85	$240.90
Purchase #5	$58.97	4.184%	$61.4373	$61.44	$61.45	$61.40
Purchase #6	$70.56	11.869%	$78.9348	$78.93	$78.95	$78.90
Purchase #7	$242.98	6.119%	$257.8479	$257.85	$257.85	$257.80
7 purchase totals =	$1,108.95		$1,200.5359	$1,200.53	$1,200.55	$1,200.50