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	$208.67	8.283%	$225.9541	$225.95	$225.95	$226.00
Purchase #2	$168.75	10.428%	$186.3473	$186.35	$186.35	$186.30
Purchase #3	$200.73	12.348%	$225.5161	$225.52	$225.50	$225.50
Purchase #4	$126.50	9.298%	$138.262	$138.26	$138.25	$138.30
Purchase #5	$214.81	6.753%	$229.3161	$229.32	$229.30	$229.30
Purchase #6	$57.46	10.174%	$63.306	$63.31	$63.30	$63.30
Purchase #7	$56.33	6.326%	$59.8934	$59.89	$59.90	$59.90
7 purchase totals =	$1,033.25		$1,128.5950	$1,128.60	$1,128.55	$1,128.60