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	$76.94	7.855%	$82.9836	$82.98	$83.00	$83.00
Purchase #2	$119.86	7.535%	$128.8915	$128.89	$128.90	$128.90
Purchase #3	$142.30	13.372%	$161.3284	$161.33	$161.35	$161.30
Purchase #4	$49.40	9.852%	$54.2669	$54.27	$54.25	$54.30
Purchase #5	$240.64	8.484%	$261.0559	$261.06	$261.05	$261.10
Purchase #6	$156.60	12.137%	$175.6065	$175.61	$175.60	$175.60
Purchase #7	$74.39	10.770%	$82.4018	$82.40	$82.40	$82.40
7 purchase totals =	$860.13		$946.5346	$946.54	$946.55	$946.60