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	$136.43	13.662%	$155.0691	$155.07	$155.05	$155.10
Purchase #2	$92.85	13.552%	$105.433	$105.43	$105.45	$105.40
Purchase #3	$156.70	3.423%	$162.0638	$162.06	$162.05	$162.10
Purchase #4	$105.70	10.730%	$117.0416	$117.04	$117.05	$117.00
Purchase #5	$167.92	11.317%	$186.9235	$186.92	$186.90	$186.90
Purchase #6	$215.82	8.219%	$233.5582	$233.56	$233.55	$233.60
Purchase #7	$141.99	4.321%	$148.1254	$148.13	$148.15	$148.10
7 purchase totals =	$1,017.41		$1,108.2146	$1,108.21	$1,108.20	$1,108.20