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	$41.43	5.857%	$43.8566	$43.86	$43.85	$43.90
Purchase #2	$6.54	13.426%	$7.4181	$7.42	$7.40	$7.40
Purchase #3	$55.63	10.604%	$61.529	$61.53	$61.55	$61.50
Purchase #4	$54.85	13.692%	$62.3601	$62.36	$62.35	$62.40
Purchase #5	$43.53	13.861%	$49.5637	$49.56	$49.55	$49.60
Purchase #6	$230.91	6.250%	$245.3419	$245.34	$245.35	$245.30
Purchase #7	$64.39	10.269%	$71.0022	$71.00	$71.00	$71.00
7 purchase totals =	$497.28		$541.0716	$541.07	$541.05	$541.10