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	$56.46	10.228%	$62.2347	$62.23	$62.25	$62.20
Purchase #2	$91.60	10.415%	$101.1401	$101.14	$101.15	$101.10
Purchase #3	$37.76	12.227%	$42.3769	$42.38	$42.40	$42.40
Purchase #4	$183.34	8.676%	$199.2466	$199.25	$199.25	$199.20
Purchase #5	$70.41	11.428%	$78.4565	$78.46	$78.45	$78.50
Purchase #6	$96.31	7.293%	$103.3339	$103.33	$103.35	$103.30
Purchase #7	$121.96	8.615%	$132.4669	$132.47	$132.45	$132.50
7 purchase totals =	$657.84		$719.2556	$719.26	$719.30	$719.20