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	$199.71	5.596%	$210.8858	$210.89	$210.90	$210.90
Purchase #2	$132.53	12.518%	$149.1201	$149.12	$149.10	$149.10
Purchase #3	$165.43	4.163%	$172.3169	$172.32	$172.30	$172.30
Purchase #4	$52.83	11.844%	$59.0872	$59.09	$59.10	$59.10
Purchase #5	$81.99	4.510%	$85.6877	$85.69	$85.70	$85.70
Purchase #6	$195.66	11.445%	$218.0533	$218.05	$218.05	$218.10
Purchase #7	$91.49	5.527%	$96.5467	$96.55	$96.55	$96.50
7 purchase totals =	$919.64		$991.6977	$991.71	$991.70	$991.70