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	$192.63	12.845%	$217.3733	$217.37	$217.35	$217.40
Purchase #2	$99.96	9.847%	$109.8031	$109.80	$109.80	$109.80
Purchase #3	$45.69	11.867%	$51.112	$51.11	$51.10	$51.10
Purchase #4	$147.46	7.338%	$158.2806	$158.28	$158.30	$158.30
Purchase #5	$64.81	5.446%	$68.3396	$68.34	$68.35	$68.30
Purchase #6	$149.39	10.511%	$165.0924	$165.09	$165.10	$165.10
Purchase #7	$175.83	13.681%	$199.8853	$199.89	$199.90	$199.90
7 purchase totals =	$875.77		$969.8863	$969.88	$969.90	$969.90