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	$238.63	11.425%	$265.8935	$265.89	$265.90	$265.90
Purchase #2	$224.83	10.851%	$249.2263	$249.23	$249.25	$249.20
Purchase #3	$24.50	13.401%	$27.7832	$27.78	$27.80	$27.80
Purchase #4	$118.63	7.296%	$127.2852	$127.29	$127.30	$127.30
Purchase #5	$161.53	9.639%	$177.0999	$177.10	$177.10	$177.10
Purchase #6	$80.26	3.271%	$82.8853	$82.89	$82.90	$82.90
Purchase #7	$127.72	13.298%	$144.7042	$144.70	$144.70	$144.70
7 purchase totals =	$976.10		$1,074.8776	$1,074.88	$1,074.95	$1,074.90