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	$205.97	8.411%	$223.2941	$223.29	$223.30	$223.30
Purchase #2	$95.59	4.408%	$99.8036	$99.80	$99.80	$99.80
Purchase #3	$69.34	12.633%	$78.0997	$78.10	$78.10	$78.10
Purchase #4	$164.60	13.590%	$186.9691	$186.97	$186.95	$187.00
Purchase #5	$168.70	6.251%	$179.2454	$179.25	$179.25	$179.20
Purchase #6	$171.33	3.470%	$177.2752	$177.28	$177.30	$177.30
Purchase #7	$132.78	6.526%	$141.4452	$141.45	$141.45	$141.40
7 purchase totals =	$1,008.31		$1,086.1323	$1,086.14	$1,086.15	$1,086.10