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	$211.49	7.451%	$227.2481	$227.25	$227.25	$227.20
Purchase #2	$13.67	10.162%	$15.0591	$15.06	$15.05	$15.10
Purchase #3	$14.49	7.452%	$15.5698	$15.57	$15.55	$15.60
Purchase #4	$24.44	12.143%	$27.4077	$27.41	$27.40	$27.40
Purchase #5	$123.44	6.207%	$131.1019	$131.10	$131.10	$131.10
Purchase #6	$59.32	3.714%	$61.5231	$61.52	$61.50	$61.50
Purchase #7	$107.71	10.362%	$118.8709	$118.87	$118.85	$118.90
7 purchase totals =	$554.56		$596.7806	$596.78	$596.70	$596.80