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	$205.80	6.629%	$219.4425	$219.44	$219.45	$219.40
Purchase #2	$63.95	6.858%	$68.3357	$68.34	$68.35	$68.30
Purchase #3	$95.30	4.757%	$99.8334	$99.83	$99.85	$99.80
Purchase #4	$248.72	3.808%	$258.1913	$258.19	$258.20	$258.20
Purchase #5	$18.73	7.466%	$20.1284	$20.13	$20.15	$20.10
Purchase #6	$186.82	11.802%	$208.8685	$208.87	$208.85	$208.90
Purchase #7	$127.83	12.786%	$144.1743	$144.17	$144.15	$144.20
7 purchase totals =	$947.15		$1,018.9741	$1,018.97	$1,019.00	$1,018.90