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	$172.86	13.574%	$196.324	$196.32	$196.30	$196.30
Purchase #2	$25.43	12.331%	$28.5658	$28.57	$28.55	$28.60
Purchase #3	$74.40	5.254%	$78.309	$78.31	$78.30	$78.30
Purchase #4	$221.93	5.644%	$234.4557	$234.46	$234.45	$234.50
Purchase #5	$178.73	4.157%	$186.1598	$186.16	$186.15	$186.20
Purchase #6	$23.82	12.589%	$26.8187	$26.82	$26.80	$26.80
Purchase #7	$238.82	8.172%	$258.3364	$258.34	$258.35	$258.30
7 purchase totals =	$935.99		$1,008.9694	$1,008.98	$1,008.90	$1,009.00