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	$234.79	11.850%	$262.6126	$262.61	$262.60	$262.60
Purchase #2	$57.56	11.608%	$64.2416	$64.24	$64.25	$64.20
Purchase #3	$177.86	4.216%	$185.3586	$185.36	$185.35	$185.40
Purchase #4	$217.96	5.284%	$229.477	$229.48	$229.50	$229.50
Purchase #5	$154.99	6.145%	$164.5141	$164.51	$164.50	$164.50
Purchase #6	$79.83	5.123%	$83.9197	$83.92	$83.90	$83.90
Purchase #7	$246.25	3.302%	$254.3812	$254.38	$254.40	$254.40
7 purchase totals =	$1,169.24		$1,244.5048	$1,244.50	$1,244.50	$1,244.50