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	$107.60	5.362%	$113.3695	$113.37	$113.35	$113.40
Purchase #2	$70.96	5.697%	$75.0026	$75.00	$75.00	$75.00
Purchase #3	$93.29	7.767%	$100.5358	$100.54	$100.55	$100.50
Purchase #4	$50.41	7.798%	$54.341	$54.34	$54.35	$54.30
Purchase #5	$22.73	13.818%	$25.8708	$25.87	$25.85	$25.90
Purchase #6	$61.60	9.169%	$67.2481	$67.25	$67.25	$67.20
Purchase #7	$247.39	11.509%	$275.8621	$275.86	$275.85	$275.90
7 purchase totals =	$653.98		$712.2299	$712.23	$712.20	$712.20