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	$128.62	10.576%	$142.2229	$142.22	$142.20	$142.20
Purchase #2	$162.27	7.591%	$174.5879	$174.59	$174.60	$174.60
Purchase #3	$19.32	13.365%	$21.9021	$21.90	$21.90	$21.90
Purchase #4	$70.97	8.371%	$76.9109	$76.91	$76.90	$76.90
Purchase #5	$50.83	11.860%	$56.8584	$56.86	$56.85	$56.90
Purchase #6	$20.38	10.712%	$22.5631	$22.56	$22.55	$22.60
Purchase #7	$171.52	6.679%	$182.9758	$182.98	$183.00	$183.00
7 purchase totals =	$623.91		$678.0211	$678.02	$678.00	$678.10