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	$247.31	4.440%	$258.2906	$258.29	$258.30	$258.30
Purchase #2	$123.85	10.368%	$136.6908	$136.69	$136.70	$136.70
Purchase #3	$45.44	6.233%	$48.2723	$48.27	$48.25	$48.30
Purchase #4	$220.32	13.749%	$250.6118	$250.61	$250.60	$250.60
Purchase #5	$131.71	9.297%	$143.9551	$143.96	$143.95	$144.00
Purchase #6	$213.39	8.852%	$232.2793	$232.28	$232.30	$232.30
Purchase #7	$37.77	13.288%	$42.7889	$42.79	$42.80	$42.80
7 purchase totals =	$1,019.79		$1,112.8888	$1,112.89	$1,112.90	$1,113.00