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	$32.82	13.476%	$37.2428	$37.24	$37.25	$37.20
Purchase #2	$249.37	13.145%	$282.1497	$282.15	$282.15	$282.10
Purchase #3	$90.60	12.114%	$101.5753	$101.58	$101.60	$101.60
Purchase #4	$109.50	7.834%	$118.0782	$118.08	$118.10	$118.10
Purchase #5	$36.97	12.458%	$41.5757	$41.58	$41.60	$41.60
Purchase #6	$151.63	10.279%	$167.216	$167.22	$167.20	$167.20
Purchase #7	$192.81	10.206%	$212.4882	$212.49	$212.50	$212.50
7 purchase totals =	$863.70		$960.3259	$960.34	$960.40	$960.30