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	$71.84	4.182%	$74.8443	$74.84	$74.85	$74.80
Purchase #2	$80.46	6.431%	$85.6344	$85.63	$85.65	$85.60
Purchase #3	$43.42	3.813%	$45.0756	$45.08	$45.10	$45.10
Purchase #4	$165.92	9.490%	$181.6658	$181.67	$181.65	$181.70
Purchase #5	$94.65	6.595%	$100.8922	$100.89	$100.90	$100.90
Purchase #6	$238.64	7.322%	$256.1132	$256.11	$256.10	$256.10
Purchase #7	$186.88	3.824%	$194.0263	$194.03	$194.05	$194.00
7 purchase totals =	$881.81		$938.2518	$938.25	$938.30	$938.20