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	$247.71	8.112%	$267.8042	$267.80	$267.80	$267.80
Purchase #2	$105.40	3.844%	$109.4516	$109.45	$109.45	$109.50
Purchase #3	$107.36	4.661%	$112.364	$112.36	$112.35	$112.40
Purchase #4	$30.57	5.188%	$32.156	$32.16	$32.15	$32.20
Purchase #5	$78.71	12.593%	$88.622	$88.62	$88.60	$88.60
Purchase #6	$241.57	5.786%	$255.5472	$255.55	$255.55	$255.50
Purchase #7	$142.45	8.102%	$153.9913	$153.99	$154.00	$154.00
7 purchase totals =	$953.77		$1,019.9363	$1,019.93	$1,019.90	$1,020.00