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	$59.67	12.603%	$67.1902	$67.19	$67.20	$67.20
Purchase #2	$157.96	6.285%	$167.8878	$167.89	$167.90	$167.90
Purchase #3	$176.69	10.351%	$194.9792	$194.98	$195.00	$195.00
Purchase #4	$13.66	5.232%	$14.3747	$14.37	$14.35	$14.40
Purchase #5	$29.45	8.850%	$32.0563	$32.06	$32.05	$32.10
Purchase #6	$137.98	13.198%	$156.1906	$156.19	$156.20	$156.20
Purchase #7	$70.26	3.722%	$72.8751	$72.88	$72.90	$72.90
7 purchase totals =	$645.67		$705.5539	$705.56	$705.60	$705.70