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	$32.76	7.305%	$35.1531	$35.15	$35.15	$35.20
Purchase #2	$99.67	7.150%	$106.7964	$106.80	$106.80	$106.80
Purchase #3	$72.45	8.175%	$78.3728	$78.37	$78.35	$78.40
Purchase #4	$84.45	5.787%	$89.3371	$89.34	$89.35	$89.30
Purchase #5	$113.71	7.184%	$121.8789	$121.88	$121.90	$121.90
Purchase #6	$84.61	7.346%	$90.8255	$90.83	$90.85	$90.80
Purchase #7	$166.29	9.674%	$182.3769	$182.38	$182.40	$182.40
7 purchase totals =	$653.94		$704.7407	$704.75	$704.80	$704.80