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	$47.39	13.815%	$53.9369	$53.94	$53.95	$53.90
Purchase #2	$53.40	10.792%	$59.1629	$59.16	$59.15	$59.20
Purchase #3	$28.89	8.126%	$31.2376	$31.24	$31.25	$31.20
Purchase #4	$201.97	8.868%	$219.8807	$219.88	$219.90	$219.90
Purchase #5	$204.97	13.832%	$233.3215	$233.32	$233.30	$233.30
Purchase #6	$67.99	6.425%	$72.3584	$72.36	$72.35	$72.40
Purchase #7	$60.56	8.679%	$65.816	$65.82	$65.80	$65.80
7 purchase totals =	$665.17		$735.7140	$735.72	$735.70	$735.70