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	$239.46	4.467%	$250.1567	$250.16	$250.15	$250.20
Purchase #2	$156.34	7.134%	$167.4933	$167.49	$167.50	$167.50
Purchase #3	$26.86	13.648%	$30.5259	$30.53	$30.55	$30.50
Purchase #4	$57.50	3.168%	$59.3216	$59.32	$59.30	$59.30
Purchase #5	$52.47	5.489%	$55.3501	$55.35	$55.35	$55.40
Purchase #6	$103.74	5.505%	$109.4509	$109.45	$109.45	$109.50
Purchase #7	$175.64	9.280%	$191.9394	$191.94	$191.95	$191.90
7 purchase totals =	$812.01		$864.2379	$864.24	$864.25	$864.30