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	$190.53	13.298%	$215.8667	$215.87	$215.85	$215.90
Purchase #2	$44.36	8.491%	$48.1266	$48.13	$48.15	$48.10
Purchase #3	$129.89	5.431%	$136.9443	$136.94	$136.95	$136.90
Purchase #4	$36.54	4.353%	$38.1306	$38.13	$38.15	$38.10
Purchase #5	$45.33	12.367%	$50.936	$50.94	$50.95	$50.90
Purchase #6	$165.96	13.230%	$187.9165	$187.92	$187.90	$187.90
Purchase #7	$63.59	11.864%	$71.1343	$71.13	$71.15	$71.10
7 purchase totals =	$676.20		$749.0550	$749.06	$749.10	$748.90