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	$231.90	3.727%	$240.5429	$240.54	$240.55	$240.50
Purchase #2	$164.45	13.410%	$186.5027	$186.50	$186.50	$186.50
Purchase #3	$28.75	13.358%	$32.5904	$32.59	$32.60	$32.60
Purchase #4	$70.83	6.296%	$75.2895	$75.29	$75.30	$75.30
Purchase #5	$102.42	7.297%	$109.8936	$109.89	$109.90	$109.90
Purchase #6	$144.80	7.766%	$156.0452	$156.05	$156.05	$156.00
Purchase #7	$225.85	12.405%	$253.8667	$253.87	$253.85	$253.90
7 purchase totals =	$969.00		$1,054.7310	$1,054.73	$1,054.75	$1,054.70