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	$205.89	7.567%	$221.4697	$221.47	$221.45	$221.50
Purchase #2	$63.93	5.614%	$67.519	$67.52	$67.50	$67.50
Purchase #3	$204.46	5.593%	$215.8954	$215.90	$215.90	$215.90
Purchase #4	$10.56	5.796%	$11.1721	$11.17	$11.15	$11.20
Purchase #5	$63.98	10.768%	$70.8694	$70.87	$70.85	$70.90
Purchase #6	$156.59	11.456%	$174.529	$174.53	$174.55	$174.50
Purchase #7	$11.28	5.204%	$11.867	$11.87	$11.85	$11.90
7 purchase totals =	$716.69		$773.3216	$773.33	$773.25	$773.40