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	$193.82	11.872%	$216.8303	$216.83	$216.85	$216.80
Purchase #2	$60.68	11.730%	$67.7978	$67.80	$67.80	$67.80
Purchase #3	$47.72	12.409%	$53.6416	$53.64	$53.65	$53.60
Purchase #4	$95.84	5.704%	$101.3067	$101.31	$101.30	$101.30
Purchase #5	$173.39	3.402%	$179.2887	$179.29	$179.30	$179.30
Purchase #6	$125.54	13.661%	$142.69	$142.69	$142.70	$142.70
Purchase #7	$114.85	4.737%	$120.2904	$120.29	$120.30	$120.30
7 purchase totals =	$811.84		$881.8455	$881.85	$881.90	$881.80