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	$166.48	13.421%	$188.8233	$188.82	$188.80	$188.80
Purchase #2	$88.91	10.510%	$98.2544	$98.25	$98.25	$98.30
Purchase #3	$240.32	12.104%	$269.4083	$269.41	$269.40	$269.40
Purchase #4	$146.41	4.874%	$153.546	$153.55	$153.55	$153.50
Purchase #5	$73.49	13.686%	$83.5478	$83.55	$83.55	$83.50
Purchase #6	$167.89	8.545%	$182.2362	$182.24	$182.25	$182.20
Purchase #7	$183.27	9.133%	$200.008	$200.01	$200.00	$200.00
7 purchase totals =	$1,066.77		$1,175.8240	$1,175.83	$1,175.80	$1,175.70