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	$92.35	5.696%	$97.6103	$97.61	$97.60	$97.60
Purchase #2	$29.83	8.371%	$32.3271	$32.33	$32.35	$32.30
Purchase #3	$10.31	5.609%	$10.8883	$10.89	$10.90	$10.90
Purchase #4	$110.96	11.408%	$123.6183	$123.62	$123.60	$123.60
Purchase #5	$104.78	11.270%	$116.5887	$116.59	$116.60	$116.60
Purchase #6	$126.47	9.366%	$138.3152	$138.32	$138.30	$138.30
Purchase #7	$26.74	5.354%	$28.1717	$28.17	$28.15	$28.20
7 purchase totals =	$501.44		$547.5196	$547.53	$547.50	$547.50