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	$205.79	13.402%	$233.37	$233.37	$233.35	$233.40
Purchase #2	$161.98	13.292%	$183.5104	$183.51	$183.50	$183.50
Purchase #3	$181.31	5.832%	$191.884	$191.88	$191.90	$191.90
Purchase #4	$87.72	5.601%	$92.6332	$92.63	$92.65	$92.60
Purchase #5	$12.86	10.670%	$14.2322	$14.23	$14.25	$14.20
Purchase #6	$56.33	4.574%	$58.9065	$58.91	$58.90	$58.90
Purchase #7	$158.31	6.665%	$168.8614	$168.86	$168.85	$168.90
7 purchase totals =	$864.30		$943.3977	$943.39	$943.40	$943.40