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	$160.67	5.551%	$169.5888	$169.59	$169.60	$169.60
Purchase #2	$190.26	5.317%	$200.3761	$200.38	$200.40	$200.40
Purchase #3	$113.28	12.268%	$127.1772	$127.18	$127.20	$127.20
Purchase #4	$210.97	6.428%	$224.5312	$224.53	$224.55	$224.50
Purchase #5	$16.90	8.170%	$18.2807	$18.28	$18.30	$18.30
Purchase #6	$175.76	3.162%	$181.3175	$181.32	$181.30	$181.30
Purchase #7	$48.53	13.765%	$55.2102	$55.21	$55.20	$55.20
7 purchase totals =	$916.37		$976.4817	$976.49	$976.55	$976.50