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	$24.47	7.665%	$26.3456	$26.35	$26.35	$26.30
Purchase #2	$159.78	5.710%	$168.9034	$168.90	$168.90	$168.90
Purchase #3	$217.47	11.408%	$242.279	$242.28	$242.30	$242.30
Purchase #4	$144.33	7.287%	$154.8473	$154.85	$154.85	$154.80
Purchase #5	$149.62	5.327%	$157.5903	$157.59	$157.60	$157.60
Purchase #6	$86.72	6.343%	$92.2206	$92.22	$92.20	$92.20
Purchase #7	$83.88	7.850%	$90.4646	$90.46	$90.45	$90.50
7 purchase totals =	$866.27		$932.6508	$932.65	$932.65	$932.60