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	$234.30	7.254%	$251.2961	$251.30	$251.30	$251.30
Purchase #2	$110.57	5.643%	$116.8095	$116.81	$116.80	$116.80
Purchase #3	$36.79	12.630%	$41.4366	$41.44	$41.45	$41.40
Purchase #4	$122.45	4.246%	$127.6492	$127.65	$127.65	$127.60
Purchase #5	$206.90	7.744%	$222.9223	$222.92	$222.90	$222.90
Purchase #6	$248.44	12.786%	$280.2055	$280.21	$280.20	$280.20
Purchase #7	$94.39	7.872%	$101.8204	$101.82	$101.80	$101.80
7 purchase totals =	$1,053.84		$1,142.1396	$1,142.15	$1,142.10	$1,142.00