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	$86.38	4.299%	$90.0935	$90.09	$90.10	$90.10
Purchase #2	$129.82	5.397%	$136.8264	$136.83	$136.85	$136.80
Purchase #3	$71.56	7.301%	$76.7846	$76.78	$76.80	$76.80
Purchase #4	$123.83	7.437%	$133.0392	$133.04	$133.05	$133.00
Purchase #5	$88.33	3.844%	$91.7254	$91.73	$91.75	$91.70
Purchase #6	$112.43	7.396%	$120.7453	$120.75	$120.75	$120.70
Purchase #7	$81.57	5.342%	$85.9275	$85.93	$85.95	$85.90
7 purchase totals =	$693.92		$735.1419	$735.15	$735.25	$735.00