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	$130.88	12.376%	$147.0777	$147.08	$147.10	$147.10
Purchase #2	$111.66	4.249%	$116.4044	$116.40	$116.40	$116.40
Purchase #3	$96.73	9.127%	$105.5585	$105.56	$105.55	$105.60
Purchase #4	$64.46	9.343%	$70.4825	$70.48	$70.50	$70.50
Purchase #5	$249.68	9.696%	$273.889	$273.89	$273.90	$273.90
Purchase #6	$76.27	5.485%	$80.4534	$80.45	$80.45	$80.50
Purchase #7	$164.93	9.646%	$180.8391	$180.84	$180.85	$180.80
7 purchase totals =	$894.61		$974.7046	$974.70	$974.75	$974.80