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	$142.90	8.570%	$155.1465	$155.15	$155.15	$155.10
Purchase #2	$150.65	11.245%	$167.5906	$167.59	$167.60	$167.60
Purchase #3	$219.70	5.121%	$230.9508	$230.95	$230.95	$231.00
Purchase #4	$178.33	11.371%	$198.6079	$198.61	$198.60	$198.60
Purchase #5	$20.81	5.389%	$21.9315	$21.93	$21.95	$21.90
Purchase #6	$198.27	12.528%	$223.1093	$223.11	$223.10	$223.10
Purchase #7	$35.97	5.308%	$37.8793	$37.88	$37.90	$37.90
7 purchase totals =	$946.63		$1,035.2159	$1,035.22	$1,035.25	$1,035.20