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	$105.25	5.513%	$111.0524	$111.05	$111.05	$111.10
Purchase #2	$59.37	3.242%	$61.2948	$61.29	$61.30	$61.30
Purchase #3	$113.39	6.571%	$120.8409	$120.84	$120.85	$120.80
Purchase #4	$58.37	12.691%	$65.7777	$65.78	$65.80	$65.80
Purchase #5	$185.62	12.132%	$208.1394	$208.14	$208.15	$208.10
Purchase #6	$125.71	7.129%	$134.6719	$134.67	$134.65	$134.70
Purchase #7	$105.56	3.264%	$109.0055	$109.01	$109.00	$109.00
7 purchase totals =	$753.27		$810.7826	$810.78	$810.80	$810.80