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	$138.74	4.475%	$144.9486	$144.95	$144.95	$144.90
Purchase #2	$141.62	6.465%	$150.7757	$150.78	$150.80	$150.80
Purchase #3	$22.89	13.488%	$25.9774	$25.98	$26.00	$26.00
Purchase #4	$80.88	12.221%	$90.7643	$90.76	$90.75	$90.80
Purchase #5	$149.96	10.598%	$165.8528	$165.85	$165.85	$165.90
Purchase #6	$245.28	7.394%	$263.416	$263.42	$263.40	$263.40
Purchase #7	$196.40	4.545%	$205.3264	$205.33	$205.35	$205.30
7 purchase totals =	$975.77		$1,047.0612	$1,047.07	$1,047.10	$1,047.10