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	$206.29	7.831%	$222.4446	$222.44	$222.45	$222.40
Purchase #2	$123.94	13.349%	$140.4848	$140.48	$140.50	$140.50
Purchase #3	$91.38	7.759%	$98.4702	$98.47	$98.45	$98.50
Purchase #4	$219.63	5.617%	$231.9666	$231.97	$231.95	$232.00
Purchase #5	$218.52	11.421%	$243.4772	$243.48	$243.50	$243.50
Purchase #6	$94.39	8.339%	$102.2612	$102.26	$102.25	$102.30
Purchase #7	$27.76	6.162%	$29.4706	$29.47	$29.45	$29.50
7 purchase totals =	$981.91		$1,068.5752	$1,068.57	$1,068.55	$1,068.70