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	$233.61	9.217%	$255.1418	$255.14	$255.15	$255.10
Purchase #2	$176.32	13.442%	$200.0209	$200.02	$200.00	$200.00
Purchase #3	$105.53	12.119%	$118.3192	$118.32	$118.30	$118.30
Purchase #4	$88.72	3.147%	$91.512	$91.51	$91.50	$91.50
Purchase #5	$197.55	6.245%	$209.887	$209.89	$209.90	$209.90
Purchase #6	$68.63	4.786%	$71.9146	$71.91	$71.90	$71.90
Purchase #7	$153.35	10.538%	$169.51	$169.51	$169.50	$169.50
7 purchase totals =	$1,023.71		$1,116.3055	$1,116.30	$1,116.25	$1,116.20