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	$97.90	13.610%	$111.2242	$111.22	$111.20	$111.20
Purchase #2	$45.47	6.656%	$48.4965	$48.50	$48.50	$48.50
Purchase #3	$116.82	5.553%	$123.307	$123.31	$123.30	$123.30
Purchase #4	$116.72	10.566%	$129.0526	$129.05	$129.05	$129.10
Purchase #5	$42.52	12.729%	$47.9324	$47.93	$47.95	$47.90
Purchase #6	$201.97	11.842%	$225.8873	$225.89	$225.90	$225.90
Purchase #7	$130.41	6.232%	$138.5372	$138.54	$138.55	$138.50
7 purchase totals =	$751.81		$824.4372	$824.44	$824.45	$824.40