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	$238.88	4.601%	$249.8709	$249.87	$249.85	$249.90
Purchase #2	$54.67	13.742%	$62.1828	$62.18	$62.20	$62.20
Purchase #3	$168.66	3.121%	$173.9239	$173.92	$173.90	$173.90
Purchase #4	$177.63	7.156%	$190.3412	$190.34	$190.35	$190.30
Purchase #5	$187.81	4.836%	$196.8925	$196.89	$196.90	$196.90
Purchase #6	$38.72	5.294%	$40.7698	$40.77	$40.75	$40.80
Purchase #7	$42.43	11.403%	$47.2683	$47.27	$47.25	$47.30
7 purchase totals =	$908.80		$961.2494	$961.24	$961.20	$961.30