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	$142.45	7.339%	$152.9044	$152.90	$152.90	$152.90
Purchase #2	$139.43	7.711%	$150.1814	$150.18	$150.20	$150.20
Purchase #3	$53.66	10.241%	$59.1553	$59.16	$59.15	$59.20
Purchase #4	$233.54	6.827%	$249.4838	$249.48	$249.50	$249.50
Purchase #5	$130.45	8.456%	$141.4809	$141.48	$141.50	$141.50
Purchase #6	$241.33	11.408%	$268.8609	$268.86	$268.85	$268.90
Purchase #7	$54.39	3.664%	$56.3828	$56.38	$56.40	$56.40
7 purchase totals =	$995.25		$1,078.4495	$1,078.44	$1,078.50	$1,078.60