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	$104.73	13.378%	$118.7408	$118.74	$118.75	$118.70
Purchase #2	$206.39	7.200%	$221.2501	$221.25	$221.25	$221.30
Purchase #3	$115.81	6.478%	$123.3122	$123.31	$123.30	$123.30
Purchase #4	$167.84	9.397%	$183.6119	$183.61	$183.60	$183.60
Purchase #5	$147.96	12.679%	$166.7198	$166.72	$166.70	$166.70
Purchase #6	$67.71	5.365%	$71.3426	$71.34	$71.35	$71.30
Purchase #7	$118.55	11.451%	$132.1252	$132.13	$132.15	$132.10
7 purchase totals =	$928.99		$1,017.1026	$1,017.10	$1,017.10	$1,017.00