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	$142.51	13.822%	$162.2077	$162.21	$162.20	$162.20
Purchase #2	$17.93	5.116%	$18.8473	$18.85	$18.85	$18.80
Purchase #3	$27.86	9.197%	$30.4223	$30.42	$30.40	$30.40
Purchase #4	$135.46	12.304%	$152.127	$152.13	$152.15	$152.10
Purchase #5	$231.32	13.539%	$262.6384	$262.64	$262.65	$262.60
Purchase #6	$40.72	4.115%	$42.3956	$42.40	$42.40	$42.40
Purchase #7	$198.81	11.586%	$221.8441	$221.84	$221.85	$221.80
7 purchase totals =	$794.61		$890.4824	$890.49	$890.50	$890.30