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	$31.83	11.538%	$35.5025	$35.50	$35.50	$35.50
Purchase #2	$43.45	9.511%	$47.5825	$47.58	$47.60	$47.60
Purchase #3	$245.75	4.813%	$257.5779	$257.58	$257.60	$257.60
Purchase #4	$208.73	6.438%	$222.168	$222.17	$222.15	$222.20
Purchase #5	$247.95	9.120%	$270.563	$270.56	$270.55	$270.60
Purchase #6	$189.85	10.355%	$209.509	$209.51	$209.50	$209.50
Purchase #7	$145.42	4.832%	$152.4467	$152.45	$152.45	$152.40
7 purchase totals =	$1,112.98		$1,195.3496	$1,195.35	$1,195.35	$1,195.40