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	$99.45	12.791%	$112.1706	$112.17	$112.15	$112.20
Purchase #2	$67.95	5.354%	$71.588	$71.59	$71.60	$71.60
Purchase #3	$217.36	7.151%	$232.9034	$232.90	$232.90	$232.90
Purchase #4	$87.71	5.619%	$92.6384	$92.64	$92.65	$92.60
Purchase #5	$92.87	3.737%	$96.3406	$96.34	$96.35	$96.30
Purchase #6	$191.62	11.826%	$214.281	$214.28	$214.30	$214.30
Purchase #7	$249.39	12.618%	$280.858	$280.86	$280.85	$280.90
7 purchase totals =	$1,006.35		$1,100.7800	$1,100.78	$1,100.80	$1,100.80