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	$112.63	11.367%	$125.4327	$125.43	$125.45	$125.40
Purchase #2	$221.98	12.387%	$249.4767	$249.48	$249.50	$249.50
Purchase #3	$66.48	9.233%	$72.6181	$72.62	$72.60	$72.60
Purchase #4	$223.29	10.114%	$245.8736	$245.87	$245.85	$245.90
Purchase #5	$201.56	11.530%	$224.7999	$224.80	$224.80	$224.80
Purchase #6	$24.82	3.679%	$25.7331	$25.73	$25.75	$25.70
Purchase #7	$69.28	13.555%	$78.6709	$78.67	$78.65	$78.70
7 purchase totals =	$920.04		$1,022.6050	$1,022.60	$1,022.60	$1,022.60