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	$28.87	11.801%	$32.2769	$32.28	$32.30	$32.30
Purchase #2	$230.72	4.844%	$241.8961	$241.90	$241.90	$241.90
Purchase #3	$93.71	11.493%	$104.4801	$104.48	$104.50	$104.50
Purchase #4	$245.32	4.824%	$257.1542	$257.15	$257.15	$257.20
Purchase #5	$249.37	11.792%	$278.7757	$278.78	$278.80	$278.80
Purchase #6	$49.59	5.251%	$52.194	$52.19	$52.20	$52.20
Purchase #7	$128.38	6.521%	$136.7517	$136.75	$136.75	$136.80
7 purchase totals =	$1,025.96		$1,103.5287	$1,103.53	$1,103.60	$1,103.70