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	$215.38	3.457%	$222.8257	$222.83	$222.85	$222.80
Purchase #2	$201.96	10.837%	$223.8464	$223.85	$223.85	$223.80
Purchase #3	$50.87	3.716%	$52.7603	$52.76	$52.75	$52.80
Purchase #4	$73.48	7.396%	$78.9146	$78.91	$78.90	$78.90
Purchase #5	$40.94	10.316%	$45.1634	$45.16	$45.15	$45.20
Purchase #6	$67.45	8.721%	$73.3323	$73.33	$73.35	$73.30
Purchase #7	$40.51	5.535%	$42.7522	$42.75	$42.75	$42.80
7 purchase totals =	$690.59		$739.5949	$739.59	$739.60	$739.60