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	$31.79	5.108%	$33.4138	$33.41	$33.40	$33.40
Purchase #2	$214.73	10.865%	$238.0604	$238.06	$238.05	$238.10
Purchase #3	$32.52	11.222%	$36.1694	$36.17	$36.15	$36.20
Purchase #4	$187.64	12.707%	$211.4834	$211.48	$211.50	$211.50
Purchase #5	$82.29	8.672%	$89.4262	$89.43	$89.45	$89.40
Purchase #6	$242.30	7.596%	$260.7051	$260.71	$260.70	$260.70
Purchase #7	$177.66	11.871%	$198.75	$198.75	$198.75	$198.80
7 purchase totals =	$968.93		$1,068.0083	$1,068.01	$1,068.00	$1,068.10