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	$103.66	9.840%	$113.8601	$113.86	$113.85	$113.90
Purchase #2	$145.58	9.504%	$159.4159	$159.42	$159.40	$159.40
Purchase #3	$136.41	5.251%	$143.5729	$143.57	$143.55	$143.60
Purchase #4	$95.51	3.507%	$98.8595	$98.86	$98.85	$98.90
Purchase #5	$62.89	6.775%	$67.1508	$67.15	$67.15	$67.20
Purchase #6	$233.71	11.435%	$260.4347	$260.43	$260.45	$260.40
Purchase #7	$223.40	13.173%	$252.8285	$252.83	$252.85	$252.80
7 purchase totals =	$1,001.16		$1,096.1224	$1,096.12	$1,096.10	$1,096.20