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	$175.36	6.330%	$186.4603	$186.46	$186.45	$186.50
Purchase #2	$238.47	6.284%	$253.4555	$253.46	$253.45	$253.50
Purchase #3	$122.44	3.851%	$127.1552	$127.16	$127.15	$127.20
Purchase #4	$244.34	5.854%	$258.6437	$258.64	$258.65	$258.60
Purchase #5	$247.58	13.797%	$281.7386	$281.74	$281.75	$281.70
Purchase #6	$125.60	4.421%	$131.1528	$131.15	$131.15	$131.20
Purchase #7	$116.59	13.473%	$132.2982	$132.30	$132.30	$132.30
7 purchase totals =	$1,270.38		$1,370.9043	$1,370.91	$1,370.90	$1,371.00