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	$34.97	9.806%	$38.3992	$38.40	$38.40	$38.40
Purchase #2	$42.75	6.541%	$45.5463	$45.55	$45.55	$45.50
Purchase #3	$51.33	4.110%	$53.4397	$53.44	$53.45	$53.40
Purchase #4	$181.27	6.390%	$192.8532	$192.85	$192.85	$192.90
Purchase #5	$168.54	12.267%	$189.2148	$189.21	$189.20	$189.20
Purchase #6	$209.41	11.478%	$233.4461	$233.45	$233.45	$233.40
Purchase #7	$138.70	9.807%	$152.3023	$152.30	$152.30	$152.30
7 purchase totals =	$826.97		$905.2016	$905.20	$905.20	$905.10