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	$167.90	13.179%	$190.0275	$190.03	$190.05	$190.00
Purchase #2	$143.86	10.849%	$159.4674	$159.47	$159.45	$159.50
Purchase #3	$52.42	9.549%	$57.4256	$57.43	$57.45	$57.40
Purchase #4	$77.95	6.803%	$83.2529	$83.25	$83.25	$83.30
Purchase #5	$173.34	4.563%	$181.2495	$181.25	$181.25	$181.20
Purchase #6	$191.91	4.337%	$200.2331	$200.23	$200.25	$200.20
Purchase #7	$51.25	5.592%	$54.1159	$54.12	$54.10	$54.10
7 purchase totals =	$858.63		$925.7719	$925.78	$925.80	$925.70