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	$218.34	6.873%	$233.3465	$233.35	$233.35	$233.30
Purchase #2	$11.40	6.222%	$12.1093	$12.11	$12.10	$12.10
Purchase #3	$219.69	13.772%	$249.9457	$249.95	$249.95	$249.90
Purchase #4	$242.38	9.583%	$265.6073	$265.61	$265.60	$265.60
Purchase #5	$140.35	11.134%	$155.9766	$155.98	$156.00	$156.00
Purchase #6	$97.44	12.262%	$109.3881	$109.39	$109.40	$109.40
Purchase #7	$35.86	5.776%	$37.9313	$37.93	$37.95	$37.90
7 purchase totals =	$965.46		$1,064.3048	$1,064.32	$1,064.35	$1,064.20