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	$246.41	10.497%	$272.2757	$272.28	$272.30	$272.30
Purchase #2	$54.28	5.822%	$57.4402	$57.44	$57.45	$57.40
Purchase #3	$147.95	11.168%	$164.4731	$164.47	$164.45	$164.50
Purchase #4	$88.43	8.395%	$95.8537	$95.85	$95.85	$95.90
Purchase #5	$148.33	9.523%	$162.4555	$162.46	$162.45	$162.50
Purchase #6	$173.58	7.267%	$186.1941	$186.19	$186.20	$186.20
Purchase #7	$80.68	12.663%	$90.8965	$90.90	$90.90	$90.90
7 purchase totals =	$939.66		$1,029.5888	$1,029.59	$1,029.60	$1,029.70