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	$147.67	3.500%	$152.8385	$152.84	$152.85	$152.80
Purchase #2	$12.26	8.295%	$13.277	$13.28	$13.30	$13.30
Purchase #3	$70.92	10.451%	$78.3318	$78.33	$78.35	$78.30
Purchase #4	$140.44	12.776%	$158.3826	$158.38	$158.40	$158.40
Purchase #5	$220.57	7.299%	$236.6694	$236.67	$236.65	$236.70
Purchase #6	$37.78	10.678%	$41.8141	$41.81	$41.80	$41.80
Purchase #7	$154.89	3.703%	$160.6256	$160.63	$160.65	$160.60
7 purchase totals =	$784.53		$841.9390	$841.94	$842.00	$841.90