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	$100.30	4.498%	$104.8115	$104.81	$104.80	$104.80
Purchase #2	$198.30	3.825%	$205.885	$205.89	$205.90	$205.90
Purchase #3	$152.40	8.367%	$165.1513	$165.15	$165.15	$165.20
Purchase #4	$111.85	12.520%	$125.8536	$125.85	$125.85	$125.90
Purchase #5	$211.76	9.776%	$232.4617	$232.46	$232.45	$232.50
Purchase #6	$182.57	7.360%	$196.0072	$196.01	$196.00	$196.00
Purchase #7	$98.83	3.508%	$102.297	$102.30	$102.30	$102.30
7 purchase totals =	$1,056.01		$1,132.4673	$1,132.47	$1,132.45	$1,132.60