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	$169.79	7.466%	$182.4665	$182.47	$182.45	$182.50
Purchase #2	$90.74	6.713%	$96.8314	$96.83	$96.85	$96.80
Purchase #3	$241.41	13.318%	$273.561	$273.56	$273.55	$273.60
Purchase #4	$162.30	10.836%	$179.8868	$179.89	$179.90	$179.90
Purchase #5	$237.49	8.254%	$257.0924	$257.09	$257.10	$257.10
Purchase #6	$146.56	6.624%	$156.2681	$156.27	$156.25	$156.30
Purchase #7	$19.52	6.360%	$20.7615	$20.76	$20.75	$20.80
7 purchase totals =	$1,067.81		$1,166.8677	$1,166.87	$1,166.85	$1,167.00