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	$112.76	9.629%	$123.6177	$123.62	$123.60	$123.60
Purchase #2	$111.43	10.771%	$123.4321	$123.43	$123.45	$123.40
Purchase #3	$202.98	6.827%	$216.8374	$216.84	$216.85	$216.80
Purchase #4	$189.86	3.211%	$195.9564	$195.96	$195.95	$196.00
Purchase #5	$81.41	10.277%	$89.7765	$89.78	$89.80	$89.80
Purchase #6	$210.76	13.804%	$239.8533	$239.85	$239.85	$239.90
Purchase #7	$190.76	11.494%	$212.686	$212.69	$212.70	$212.70
7 purchase totals =	$1,099.96		$1,202.1594	$1,202.17	$1,202.20	$1,202.20