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	$211.50	12.479%	$237.8931	$237.89	$237.90	$237.90
Purchase #2	$82.76	9.560%	$90.6719	$90.67	$90.65	$90.70
Purchase #3	$43.54	11.138%	$48.3895	$48.39	$48.40	$48.40
Purchase #4	$6.92	8.179%	$7.486	$7.49	$7.50	$7.50
Purchase #5	$210.53	3.847%	$218.6291	$218.63	$218.65	$218.60
Purchase #6	$156.76	4.820%	$164.3158	$164.32	$164.30	$164.30
Purchase #7	$164.45	11.642%	$183.5953	$183.60	$183.60	$183.60
7 purchase totals =	$876.46		$950.9807	$950.99	$951.00	$951.00