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	$248.47	7.666%	$267.5177	$267.52	$267.50	$267.50
Purchase #2	$96.60	7.534%	$103.8778	$103.88	$103.90	$103.90
Purchase #3	$230.52	8.440%	$249.9759	$249.98	$250.00	$250.00
Purchase #4	$96.46	8.446%	$104.607	$104.61	$104.60	$104.60
Purchase #5	$151.81	5.636%	$160.366	$160.37	$160.35	$160.40
Purchase #6	$230.90	3.118%	$238.0995	$238.10	$238.10	$238.10
Purchase #7	$90.82	11.363%	$101.1399	$101.14	$101.15	$101.10
7 purchase totals =	$1,145.58		$1,225.5838	$1,225.60	$1,225.60	$1,225.60