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	$77.63	10.363%	$85.6748	$85.67	$85.65	$85.70
Purchase #2	$40.27	4.309%	$42.0052	$42.01	$42.00	$42.00
Purchase #3	$134.61	10.155%	$148.2796	$148.28	$148.30	$148.30
Purchase #4	$238.36	11.208%	$265.0754	$265.08	$265.10	$265.10
Purchase #5	$19.32	6.607%	$20.5965	$20.60	$20.60	$20.60
Purchase #6	$117.75	10.304%	$129.883	$129.88	$129.90	$129.90
Purchase #7	$95.39	8.284%	$103.2921	$103.29	$103.30	$103.30
7 purchase totals =	$723.33		$794.8066	$794.81	$794.85	$794.90