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	$55.57	6.186%	$59.0076	$59.01	$59.00	$59.00
Purchase #2	$83.64	9.168%	$91.3081	$91.31	$91.30	$91.30
Purchase #3	$103.60	3.246%	$106.9629	$106.96	$106.95	$107.00
Purchase #4	$223.93	11.824%	$250.4075	$250.41	$250.40	$250.40
Purchase #5	$124.91	12.468%	$140.4838	$140.48	$140.50	$140.50
Purchase #6	$199.75	11.574%	$222.8691	$222.87	$222.85	$222.90
Purchase #7	$182.48	12.857%	$205.9415	$205.94	$205.95	$205.90
7 purchase totals =	$973.88		$1,076.9805	$1,076.98	$1,076.95	$1,077.00