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	$196.28	13.346%	$222.4755	$222.48	$222.50	$222.50
Purchase #2	$41.98	12.873%	$47.3841	$47.38	$47.40	$47.40
Purchase #3	$36.78	5.263%	$38.7157	$38.72	$38.70	$38.70
Purchase #4	$37.52	4.681%	$39.2763	$39.28	$39.30	$39.30
Purchase #5	$120.87	12.855%	$136.4078	$136.41	$136.40	$136.40
Purchase #6	$181.31	7.415%	$194.7541	$194.75	$194.75	$194.80
Purchase #7	$136.47	11.750%	$152.5052	$152.51	$152.50	$152.50
7 purchase totals =	$751.21		$831.5187	$831.53	$831.55	$831.60