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	$65.52	11.637%	$73.1446	$73.14	$73.15	$73.10
Purchase #2	$97.63	11.746%	$109.0976	$109.10	$109.10	$109.10
Purchase #3	$63.49	6.145%	$67.3915	$67.39	$67.40	$67.40
Purchase #4	$93.59	10.691%	$103.5957	$103.60	$103.60	$103.60
Purchase #5	$157.70	10.687%	$174.5534	$174.55	$174.55	$174.60
Purchase #6	$7.57	11.834%	$8.4658	$8.47	$8.45	$8.50
Purchase #7	$61.86	6.222%	$65.7089	$65.71	$65.70	$65.70
7 purchase totals =	$547.36		$601.9575	$601.96	$601.95	$602.00