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	$221.44	12.407%	$248.9141	$248.91	$248.90	$248.90
Purchase #2	$60.74	11.818%	$67.9183	$67.92	$67.90	$67.90
Purchase #3	$37.46	10.212%	$41.2854	$41.29	$41.30	$41.30
Purchase #4	$192.63	12.306%	$216.335	$216.34	$216.35	$216.30
Purchase #5	$203.34	6.658%	$216.8784	$216.88	$216.90	$216.90
Purchase #6	$40.83	4.285%	$42.5796	$42.58	$42.60	$42.60
Purchase #7	$125.43	12.789%	$141.4712	$141.47	$141.45	$141.50
7 purchase totals =	$881.87		$975.3820	$975.39	$975.40	$975.40