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	$80.25	4.194%	$83.6157	$83.62	$83.60	$83.60
Purchase #2	$33.74	11.274%	$37.5438	$37.54	$37.55	$37.50
Purchase #3	$36.51	5.438%	$38.4954	$38.50	$38.50	$38.50
Purchase #4	$35.85	4.369%	$37.4163	$37.42	$37.40	$37.40
Purchase #5	$209.70	6.138%	$222.5714	$222.57	$222.55	$222.60
Purchase #6	$142.49	3.651%	$147.6923	$147.69	$147.70	$147.70
Purchase #7	$162.72	10.437%	$179.7031	$179.70	$179.70	$179.70
7 purchase totals =	$701.26		$747.0380	$747.04	$747.00	$747.00