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	$248.97	4.400%	$259.9247	$259.92	$259.90	$259.90
Purchase #2	$160.72	5.128%	$168.9617	$168.96	$168.95	$169.00
Purchase #3	$237.61	11.534%	$265.0159	$265.02	$265.00	$265.00
Purchase #4	$52.32	4.121%	$54.4761	$54.48	$54.50	$54.50
Purchase #5	$175.71	5.642%	$185.6236	$185.62	$185.60	$185.60
Purchase #6	$56.86	3.387%	$58.7858	$58.79	$58.80	$58.80
Purchase #7	$106.94	10.723%	$118.4072	$118.41	$118.40	$118.40
7 purchase totals =	$1,039.13		$1,111.1950	$1,111.20	$1,111.15	$1,111.20