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	$86.83	13.599%	$98.638	$98.64	$98.65	$98.60
Purchase #2	$89.83	12.329%	$100.9051	$100.91	$100.90	$100.90
Purchase #3	$195.96	10.355%	$216.2517	$216.25	$216.25	$216.30
Purchase #4	$212.67	4.129%	$221.4511	$221.45	$221.45	$221.50
Purchase #5	$150.55	13.108%	$170.2841	$170.28	$170.30	$170.30
Purchase #6	$138.58	4.354%	$144.6138	$144.61	$144.60	$144.60
Purchase #7	$210.59	6.526%	$224.3331	$224.33	$224.35	$224.30
7 purchase totals =	$1,085.01		$1,176.4769	$1,176.47	$1,176.50	$1,176.50