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	$168.82	11.517%	$188.263	$188.26	$188.25	$188.30
Purchase #2	$157.64	5.796%	$166.7768	$166.78	$166.80	$166.80
Purchase #3	$213.76	11.800%	$238.9837	$238.98	$239.00	$239.00
Purchase #4	$229.27	6.698%	$244.6265	$244.63	$244.65	$244.60
Purchase #5	$246.49	13.845%	$280.6165	$280.62	$280.60	$280.60
Purchase #6	$80.92	5.485%	$85.3585	$85.36	$85.35	$85.40
Purchase #7	$89.80	6.818%	$95.9226	$95.92	$95.90	$95.90
7 purchase totals =	$1,186.70		$1,300.5476	$1,300.55	$1,300.55	$1,300.60