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	$176.37	4.833%	$184.894	$184.89	$184.90	$184.90
Purchase #2	$211.92	5.596%	$223.779	$223.78	$223.80	$223.80
Purchase #3	$68.90	13.295%	$78.0603	$78.06	$78.05	$78.10
Purchase #4	$25.25	11.870%	$28.2472	$28.25	$28.25	$28.20
Purchase #5	$44.81	13.265%	$50.754	$50.75	$50.75	$50.80
Purchase #6	$101.39	8.388%	$109.8946	$109.89	$109.90	$109.90
Purchase #7	$157.31	3.199%	$162.3423	$162.34	$162.35	$162.30
7 purchase totals =	$785.95		$837.9714	$837.96	$838.00	$838.00