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	$236.84	7.619%	$254.8848	$254.88	$254.90	$254.90
Purchase #2	$13.95	7.528%	$15.0002	$15.00	$15.00	$15.00
Purchase #3	$21.49	9.166%	$23.4598	$23.46	$23.45	$23.50
Purchase #4	$46.40	13.183%	$52.5169	$52.52	$52.50	$52.50
Purchase #5	$94.36	6.677%	$100.6604	$100.66	$100.65	$100.70
Purchase #6	$67.86	6.134%	$72.0225	$72.02	$72.00	$72.00
Purchase #7	$223.73	4.347%	$233.4555	$233.46	$233.45	$233.50
7 purchase totals =	$704.63		$752.0001	$752.00	$751.95	$752.10