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	$134.44	13.719%	$152.8838	$152.88	$152.90	$152.90
Purchase #2	$213.38	9.402%	$233.442	$233.44	$233.45	$233.40
Purchase #3	$126.65	7.694%	$136.3945	$136.39	$136.40	$136.40
Purchase #4	$96.67	7.723%	$104.1358	$104.14	$104.15	$104.10
Purchase #5	$180.83	3.318%	$186.8299	$186.83	$186.85	$186.80
Purchase #6	$57.78	13.471%	$65.5635	$65.56	$65.55	$65.60
Purchase #7	$237.92	10.466%	$262.8207	$262.82	$262.80	$262.80
7 purchase totals =	$1,047.67		$1,142.0702	$1,142.06	$1,142.10	$1,142.00