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	$107.50	3.328%	$111.0776	$111.08	$111.10	$111.10
Purchase #2	$170.43	12.591%	$191.8888	$191.89	$191.90	$191.90
Purchase #3	$88.54	12.285%	$99.4171	$99.42	$99.40	$99.40
Purchase #4	$83.29	5.291%	$87.6969	$87.70	$87.70	$87.70
Purchase #5	$216.55	4.116%	$225.4632	$225.46	$225.45	$225.50
Purchase #6	$42.35	12.657%	$47.7102	$47.71	$47.70	$47.70
Purchase #7	$169.82	6.423%	$180.7275	$180.73	$180.75	$180.70
7 purchase totals =	$878.48		$943.9813	$943.99	$944.00	$944.00