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	$233.56	13.470%	$265.0205	$265.02	$265.00	$265.00
Purchase #2	$134.40	11.849%	$150.3251	$150.33	$150.35	$150.30
Purchase #3	$186.72	6.418%	$198.7037	$198.70	$198.70	$198.70
Purchase #4	$105.29	4.308%	$109.8259	$109.83	$109.85	$109.80
Purchase #5	$240.47	13.776%	$273.5971	$273.60	$273.60	$273.60
Purchase #6	$83.60	4.649%	$87.4866	$87.49	$87.50	$87.50
Purchase #7	$180.87	8.566%	$196.3633	$196.36	$196.35	$196.40
7 purchase totals =	$1,164.91		$1,281.3222	$1,281.33	$1,281.35	$1,281.30