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	$134.55	5.642%	$142.1413	$142.14	$142.15	$142.10
Purchase #2	$89.31	13.130%	$101.0364	$101.04	$101.05	$101.00
Purchase #3	$181.57	10.305%	$200.2808	$200.28	$200.30	$200.30
Purchase #4	$57.77	3.109%	$59.5661	$59.57	$59.55	$59.60
Purchase #5	$24.47	4.628%	$25.6025	$25.60	$25.60	$25.60
Purchase #6	$18.86	4.811%	$19.7674	$19.77	$19.75	$19.80
Purchase #7	$113.79	4.453%	$118.8571	$118.86	$118.85	$118.90
7 purchase totals =	$620.32		$667.2516	$667.26	$667.25	$667.30