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	$150.59	13.737%	$171.2765	$171.28	$171.30	$171.30
Purchase #2	$57.34	7.359%	$61.5597	$61.56	$61.55	$61.60
Purchase #3	$151.42	11.262%	$168.4729	$168.47	$168.45	$168.50
Purchase #4	$47.93	9.514%	$52.4901	$52.49	$52.50	$52.50
Purchase #5	$33.27	13.607%	$37.797	$37.80	$37.80	$37.80
Purchase #6	$205.66	4.857%	$215.6489	$215.65	$215.65	$215.60
Purchase #7	$236.79	10.136%	$260.791	$260.79	$260.80	$260.80
7 purchase totals =	$883.00		$968.0361	$968.04	$968.05	$968.10