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	$96.32	13.757%	$109.5707	$109.57	$109.55	$109.60
Purchase #2	$47.76	4.408%	$49.8653	$49.87	$49.85	$49.90
Purchase #3	$136.36	6.571%	$145.3202	$145.32	$145.30	$145.30
Purchase #4	$80.85	8.104%	$87.4021	$87.40	$87.40	$87.40
Purchase #5	$167.39	7.836%	$180.5067	$180.51	$180.50	$180.50
Purchase #6	$248.31	6.681%	$264.8996	$264.90	$264.90	$264.90
Purchase #7	$91.79	3.475%	$94.9797	$94.98	$95.00	$95.00
7 purchase totals =	$868.78		$932.5443	$932.55	$932.50	$932.60