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	$193.55	10.495%	$213.8631	$213.86	$213.85	$213.90
Purchase #2	$177.62	5.520%	$187.4246	$187.42	$187.40	$187.40
Purchase #3	$40.72	11.434%	$45.3759	$45.38	$45.40	$45.40
Purchase #4	$136.53	13.420%	$154.8523	$154.85	$154.85	$154.90
Purchase #5	$18.40	10.151%	$20.2678	$20.27	$20.25	$20.30
Purchase #6	$201.85	6.599%	$215.1701	$215.17	$215.15	$215.20
Purchase #7	$152.49	11.362%	$169.8159	$169.82	$169.80	$169.80
7 purchase totals =	$921.16		$1,006.7697	$1,006.77	$1,006.70	$1,006.90