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	$144.97	5.455%	$152.8781	$152.88	$152.90	$152.90
Purchase #2	$53.89	10.213%	$59.3938	$59.39	$59.40	$59.40
Purchase #3	$38.68	6.148%	$41.058	$41.06	$41.05	$41.10
Purchase #4	$164.26	12.853%	$185.3723	$185.37	$185.35	$185.40
Purchase #5	$156.90	6.652%	$167.337	$167.34	$167.35	$167.30
Purchase #6	$98.57	13.625%	$112.0002	$112.00	$112.00	$112.00
Purchase #7	$141.96	3.628%	$147.1103	$147.11	$147.10	$147.10
7 purchase totals =	$799.23		$865.1497	$865.15	$865.15	$865.20