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	$30.49	11.187%	$33.9009	$33.90	$33.90	$33.90
Purchase #2	$123.27	9.403%	$134.8611	$134.86	$134.85	$134.90
Purchase #3	$146.32	4.334%	$152.6615	$152.66	$152.65	$152.70
Purchase #4	$173.41	11.519%	$193.3851	$193.39	$193.40	$193.40
Purchase #5	$46.80	4.369%	$48.8447	$48.84	$48.85	$48.80
Purchase #6	$183.89	6.641%	$196.1021	$196.10	$196.10	$196.10
Purchase #7	$113.92	3.450%	$117.8502	$117.85	$117.85	$117.90
7 purchase totals =	$818.10		$877.6056	$877.60	$877.60	$877.70