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	$145.70	11.807%	$162.9028	$162.90	$162.90	$162.90
Purchase #2	$82.59	3.160%	$85.1998	$85.20	$85.20	$85.20
Purchase #3	$14.71	13.434%	$16.6861	$16.69	$16.70	$16.70
Purchase #4	$75.81	12.317%	$85.1475	$85.15	$85.15	$85.10
Purchase #5	$147.35	13.774%	$167.646	$167.65	$167.65	$167.60
Purchase #6	$228.50	5.166%	$240.3043	$240.30	$240.30	$240.30
Purchase #7	$182.83	3.111%	$188.5178	$188.52	$188.50	$188.50
7 purchase totals =	$877.49		$946.4043	$946.41	$946.40	$946.30