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	$116.59	11.169%	$129.6119	$129.61	$129.60	$129.60
Purchase #2	$67.28	9.703%	$73.8082	$73.81	$73.80	$73.80
Purchase #3	$57.46	10.388%	$63.4289	$63.43	$63.45	$63.40
Purchase #4	$190.57	11.419%	$212.3312	$212.33	$212.35	$212.30
Purchase #5	$61.28	9.456%	$67.0746	$67.07	$67.05	$67.10
Purchase #6	$105.82	5.223%	$111.347	$111.35	$111.35	$111.30
Purchase #7	$98.89	13.240%	$111.983	$111.98	$112.00	$112.00
7 purchase totals =	$697.89		$769.5848	$769.58	$769.60	$769.50