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	$217.99	11.672%	$243.4338	$243.43	$243.45	$243.40
Purchase #2	$81.57	4.543%	$85.2757	$85.28	$85.30	$85.30
Purchase #3	$78.25	7.719%	$84.2901	$84.29	$84.30	$84.30
Purchase #4	$144.32	10.816%	$159.9297	$159.93	$159.95	$159.90
Purchase #5	$116.97	5.554%	$123.4665	$123.47	$123.45	$123.50
Purchase #6	$229.90	9.588%	$251.9428	$251.94	$251.95	$251.90
Purchase #7	$95.80	7.636%	$103.1153	$103.12	$103.10	$103.10
7 purchase totals =	$964.80		$1,051.4539	$1,051.46	$1,051.50	$1,051.40