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	$184.65	3.153%	$190.472	$190.47	$190.45	$190.50
Purchase #2	$242.65	10.685%	$268.5772	$268.58	$268.60	$268.60
Purchase #3	$151.45	5.301%	$159.4784	$159.48	$159.50	$159.50
Purchase #4	$65.41	7.690%	$70.44	$70.44	$70.45	$70.40
Purchase #5	$188.27	12.800%	$212.3686	$212.37	$212.35	$212.40
Purchase #6	$165.26	5.648%	$174.5939	$174.59	$174.60	$174.60
Purchase #7	$63.91	4.315%	$66.6677	$66.67	$66.65	$66.70
7 purchase totals =	$1,061.60		$1,142.5978	$1,142.60	$1,142.60	$1,142.70