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	$178.73	10.172%	$196.9104	$196.91	$196.90	$196.90
Purchase #2	$57.49	8.494%	$62.3732	$62.37	$62.35	$62.40
Purchase #3	$163.81	7.330%	$175.8173	$175.82	$175.80	$175.80
Purchase #4	$228.65	8.822%	$248.8215	$248.82	$248.80	$248.80
Purchase #5	$28.71	9.430%	$31.4174	$31.42	$31.40	$31.40
Purchase #6	$56.31	11.716%	$62.9073	$62.91	$62.90	$62.90
Purchase #7	$48.74	7.679%	$52.4827	$52.48	$52.50	$52.50
7 purchase totals =	$762.44		$830.7298	$830.73	$830.65	$830.70