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	$134.59	7.269%	$144.3733	$144.37	$144.35	$144.40
Purchase #2	$10.92	10.352%	$12.0504	$12.05	$12.05	$12.10
Purchase #3	$205.36	9.749%	$225.3805	$225.38	$225.40	$225.40
Purchase #4	$96.72	7.454%	$103.9295	$103.93	$103.95	$103.90
Purchase #5	$148.77	7.634%	$160.1271	$160.13	$160.15	$160.10
Purchase #6	$129.46	8.710%	$140.736	$140.74	$140.75	$140.70
Purchase #7	$72.59	13.534%	$82.4143	$82.41	$82.40	$82.40
7 purchase totals =	$798.41		$869.0111	$869.01	$869.05	$869.00