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	$35.48	5.457%	$37.4161	$37.42	$37.40	$37.40
Purchase #2	$130.66	4.541%	$136.5933	$136.59	$136.60	$136.60
Purchase #3	$201.38	4.537%	$210.5166	$210.52	$210.50	$210.50
Purchase #4	$233.25	4.703%	$244.2197	$244.22	$244.20	$244.20
Purchase #5	$151.71	10.781%	$168.0659	$168.07	$168.05	$168.10
Purchase #6	$80.41	12.662%	$90.5915	$90.59	$90.60	$90.60
Purchase #7	$212.76	10.776%	$235.687	$235.69	$235.70	$235.70
7 purchase totals =	$1,045.65		$1,123.0901	$1,123.10	$1,123.05	$1,123.10