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	$147.76	13.580%	$167.8258	$167.83	$167.85	$167.80
Purchase #2	$39.45	5.766%	$41.7247	$41.72	$41.70	$41.70
Purchase #3	$24.52	4.382%	$25.5945	$25.59	$25.60	$25.60
Purchase #4	$10.96	12.441%	$12.3235	$12.32	$12.30	$12.30
Purchase #5	$202.29	8.499%	$219.4826	$219.48	$219.50	$219.50
Purchase #6	$35.63	11.181%	$39.6138	$39.61	$39.60	$39.60
Purchase #7	$144.71	5.301%	$152.3811	$152.38	$152.40	$152.40
7 purchase totals =	$605.32		$658.9460	$658.93	$658.95	$658.90