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	$179.26	5.573%	$189.2502	$189.25	$189.25	$189.30
Purchase #2	$55.77	6.235%	$59.2473	$59.25	$59.25	$59.20
Purchase #3	$7.33	7.363%	$7.8697	$7.87	$7.85	$7.90
Purchase #4	$66.67	10.273%	$73.519	$73.52	$73.50	$73.50
Purchase #5	$155.39	7.483%	$167.0178	$167.02	$167.00	$167.00
Purchase #6	$124.90	7.386%	$134.1251	$134.13	$134.15	$134.10
Purchase #7	$59.72	12.488%	$67.1778	$67.18	$67.20	$67.20
7 purchase totals =	$649.04		$698.2069	$698.22	$698.20	$698.20