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	$157.51	3.203%	$162.555	$162.56	$162.55	$162.60
Purchase #2	$181.33	13.266%	$205.3852	$205.39	$205.40	$205.40
Purchase #3	$114.43	8.325%	$123.9563	$123.96	$123.95	$124.00
Purchase #4	$14.26	9.772%	$15.6535	$15.65	$15.65	$15.70
Purchase #5	$55.54	7.774%	$59.8577	$59.86	$59.85	$59.90
Purchase #6	$189.40	11.868%	$211.878	$211.88	$211.90	$211.90
Purchase #7	$24.37	12.838%	$27.4986	$27.50	$27.50	$27.50
7 purchase totals =	$736.84		$806.7843	$806.80	$806.80	$807.00