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	$168.56	3.520%	$174.4933	$174.49	$174.50	$174.50
Purchase #2	$157.46	3.205%	$162.5066	$162.51	$162.50	$162.50
Purchase #3	$236.81	7.866%	$255.4375	$255.44	$255.45	$255.40
Purchase #4	$157.37	13.767%	$179.0351	$179.04	$179.05	$179.00
Purchase #5	$206.77	4.164%	$215.3799	$215.38	$215.40	$215.40
Purchase #6	$234.31	13.292%	$265.4545	$265.45	$265.45	$265.50
Purchase #7	$160.62	4.481%	$167.8174	$167.82	$167.80	$167.80
7 purchase totals =	$1,321.90		$1,420.1243	$1,420.13	$1,420.15	$1,420.10