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	$162.88	13.669%	$185.1441	$185.14	$185.15	$185.10
Purchase #2	$29.34	12.855%	$33.1117	$33.11	$33.10	$33.10
Purchase #3	$97.55	10.356%	$107.6523	$107.65	$107.65	$107.70
Purchase #4	$82.60	10.556%	$91.3193	$91.32	$91.30	$91.30
Purchase #5	$71.75	13.339%	$81.3207	$81.32	$81.30	$81.30
Purchase #6	$215.47	5.652%	$227.6484	$227.65	$227.65	$227.60
Purchase #7	$32.77	3.312%	$33.8553	$33.86	$33.85	$33.90
7 purchase totals =	$692.36		$760.0518	$760.05	$760.00	$760.00