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	$135.60	13.224%	$153.5317	$153.53	$153.55	$153.50
Purchase #2	$180.90	10.862%	$200.5494	$200.55	$200.55	$200.50
Purchase #3	$234.93	3.725%	$243.6811	$243.68	$243.70	$243.70
Purchase #4	$11.26	6.375%	$11.9778	$11.98	$12.00	$12.00
Purchase #5	$13.77	11.310%	$15.3274	$15.33	$15.35	$15.30
Purchase #6	$169.32	9.418%	$185.2666	$185.27	$185.25	$185.30
Purchase #7	$39.50	8.141%	$42.7157	$42.72	$42.70	$42.70
7 purchase totals =	$785.28		$853.0497	$853.06	$853.10	$853.00