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	$169.58	10.207%	$186.889	$186.89	$186.90	$186.90
Purchase #2	$95.53	4.226%	$99.5671	$99.57	$99.55	$99.60
Purchase #3	$89.81	11.860%	$100.4615	$100.46	$100.45	$100.50
Purchase #4	$116.65	5.353%	$122.8943	$122.89	$122.90	$122.90
Purchase #5	$122.81	3.415%	$127.004	$127.00	$127.00	$127.00
Purchase #6	$61.76	13.368%	$70.0161	$70.02	$70.00	$70.00
Purchase #7	$7.39	9.495%	$8.0917	$8.09	$8.10	$8.10
7 purchase totals =	$663.53		$714.9237	$714.92	$714.90	$715.00