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	$35.39	5.760%	$37.4285	$37.43	$37.45	$37.40
Purchase #2	$55.79	7.245%	$59.832	$59.83	$59.85	$59.80
Purchase #3	$110.54	6.586%	$117.8202	$117.82	$117.80	$117.80
Purchase #4	$172.49	8.301%	$186.8084	$186.81	$186.80	$186.80
Purchase #5	$153.75	8.191%	$166.3437	$166.34	$166.35	$166.30
Purchase #6	$120.82	7.510%	$129.8936	$129.89	$129.90	$129.90
Purchase #7	$242.25	5.297%	$255.082	$255.08	$255.10	$255.10
7 purchase totals =	$891.03		$953.2084	$953.20	$953.25	$953.10