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	$190.41	4.737%	$199.4297	$199.43	$199.45	$199.40
Purchase #2	$134.84	7.330%	$144.7238	$144.72	$144.70	$144.70
Purchase #3	$135.80	6.533%	$144.6718	$144.67	$144.65	$144.70
Purchase #4	$75.32	6.411%	$80.1488	$80.15	$80.15	$80.10
Purchase #5	$209.82	12.343%	$235.7181	$235.72	$235.70	$235.70
Purchase #6	$137.99	3.524%	$142.8528	$142.85	$142.85	$142.90
Purchase #7	$50.51	9.111%	$55.112	$55.11	$55.10	$55.10
7 purchase totals =	$934.69		$1,002.6570	$1,002.65	$1,002.60	$1,002.60