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	$125.51	13.676%	$142.6747	$142.67	$142.65	$142.70
Purchase #2	$78.81	8.550%	$85.5483	$85.55	$85.55	$85.50
Purchase #3	$199.42	13.307%	$225.9568	$225.96	$225.95	$226.00
Purchase #4	$85.85	8.162%	$92.8571	$92.86	$92.85	$92.90
Purchase #5	$104.46	8.309%	$113.1396	$113.14	$113.15	$113.10
Purchase #6	$239.74	13.769%	$272.7498	$272.75	$272.75	$272.70
Purchase #7	$92.72	7.334%	$99.5201	$99.52	$99.50	$99.50
7 purchase totals =	$926.51		$1,032.4464	$1,032.45	$1,032.40	$1,032.40