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	$165.59	3.485%	$171.3608	$171.36	$171.35	$171.40
Purchase #2	$76.85	13.548%	$87.2616	$87.26	$87.25	$87.30
Purchase #3	$117.66	6.521%	$125.3326	$125.33	$125.35	$125.30
Purchase #4	$43.77	3.203%	$45.172	$45.17	$45.15	$45.20
Purchase #5	$162.86	9.524%	$178.3708	$178.37	$178.35	$178.40
Purchase #6	$22.89	6.429%	$24.3616	$24.36	$24.35	$24.40
Purchase #7	$28.54	10.305%	$31.481	$31.48	$31.50	$31.50
7 purchase totals =	$618.16		$663.3404	$663.33	$663.30	$663.50