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	$67.86	8.847%	$73.8636	$73.86	$73.85	$73.90
Purchase #2	$92.76	6.753%	$99.0241	$99.02	$99.00	$99.00
Purchase #3	$40.89	6.231%	$43.4379	$43.44	$43.45	$43.40
Purchase #4	$210.35	7.323%	$225.7539	$225.75	$225.75	$225.80
Purchase #5	$151.36	5.321%	$159.4139	$159.41	$159.40	$159.40
Purchase #6	$199.33	9.148%	$217.5647	$217.56	$217.55	$217.60
Purchase #7	$11.26	10.635%	$12.4575	$12.46	$12.45	$12.50
7 purchase totals =	$773.81		$831.5156	$831.50	$831.45	$831.60