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	$33.64	11.365%	$37.4632	$37.46	$37.45	$37.50
Purchase #2	$59.45	13.631%	$67.5536	$67.55	$67.55	$67.60
Purchase #3	$43.33	6.646%	$46.2097	$46.21	$46.20	$46.20
Purchase #4	$138.36	10.834%	$153.3499	$153.35	$153.35	$153.30
Purchase #5	$224.68	10.195%	$247.5861	$247.59	$247.60	$247.60
Purchase #6	$173.52	3.537%	$179.6574	$179.66	$179.65	$179.70
Purchase #7	$88.47	3.693%	$91.7372	$91.74	$91.75	$91.70
7 purchase totals =	$761.45		$823.5571	$823.56	$823.55	$823.60