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	$70.65	5.441%	$74.4941	$74.49	$74.50	$74.50
Purchase #2	$218.25	4.395%	$227.8421	$227.84	$227.85	$227.80
Purchase #3	$32.47	9.271%	$35.4803	$35.48	$35.50	$35.50
Purchase #4	$205.28	8.788%	$223.32	$223.32	$223.30	$223.30
Purchase #5	$96.80	7.508%	$104.0677	$104.07	$104.05	$104.10
Purchase #6	$162.56	4.296%	$169.5436	$169.54	$169.55	$169.50
Purchase #7	$236.72	7.238%	$253.8538	$253.85	$253.85	$253.90
7 purchase totals =	$1,022.73		$1,088.6016	$1,088.59	$1,088.60	$1,088.60