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	$99.73	11.316%	$111.0154	$111.02	$111.00	$111.00
Purchase #2	$13.45	13.138%	$15.2171	$15.22	$15.20	$15.20
Purchase #3	$162.82	10.782%	$180.3753	$180.38	$180.40	$180.40
Purchase #4	$37.96	3.350%	$39.2317	$39.23	$39.25	$39.20
Purchase #5	$125.44	7.536%	$134.8932	$134.89	$134.90	$134.90
Purchase #6	$186.76	5.365%	$196.7797	$196.78	$196.80	$196.80
Purchase #7	$21.35	8.446%	$23.1532	$23.15	$23.15	$23.20
7 purchase totals =	$647.51		$700.6656	$700.67	$700.70	$700.70