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	$211.41	5.444%	$222.9192	$222.92	$222.90	$222.90
Purchase #2	$165.40	10.231%	$182.3221	$182.32	$182.30	$182.30
Purchase #3	$15.92	10.785%	$17.637	$17.64	$17.65	$17.60
Purchase #4	$211.41	3.675%	$219.1793	$219.18	$219.20	$219.20
Purchase #5	$31.96	9.143%	$34.8821	$34.88	$34.90	$34.90
Purchase #6	$127.40	13.392%	$144.4614	$144.46	$144.45	$144.50
Purchase #7	$250.43	3.144%	$258.3035	$258.30	$258.30	$258.30
7 purchase totals =	$1,013.93		$1,079.7046	$1,079.70	$1,079.70	$1,079.70