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	$36.48	12.227%	$40.9404	$40.94	$40.95	$40.90
Purchase #2	$115.53	3.411%	$119.4707	$119.47	$119.45	$119.50
Purchase #3	$73.93	5.441%	$77.9525	$77.95	$77.95	$78.00
Purchase #4	$131.66	13.616%	$149.5868	$149.59	$149.60	$149.60
Purchase #5	$19.85	5.240%	$20.8901	$20.89	$20.90	$20.90
Purchase #6	$168.32	6.512%	$179.281	$179.28	$179.30	$179.30
Purchase #7	$111.56	9.816%	$122.5107	$122.51	$122.50	$122.50
7 purchase totals =	$657.33		$710.6322	$710.63	$710.65	$710.70