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	$40.83	3.517%	$42.266	$42.27	$42.25	$42.30
Purchase #2	$33.39	11.293%	$37.1607	$37.16	$37.15	$37.20
Purchase #3	$167.83	12.738%	$189.2082	$189.21	$189.20	$189.20
Purchase #4	$156.33	12.594%	$176.0182	$176.02	$176.00	$176.00
Purchase #5	$195.91	10.376%	$216.2376	$216.24	$216.25	$216.20
Purchase #6	$37.37	11.247%	$41.573	$41.57	$41.55	$41.60
Purchase #7	$140.92	6.488%	$150.0629	$150.06	$150.05	$150.10
7 purchase totals =	$772.58		$852.5266	$852.53	$852.45	$852.60