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	$218.46	3.439%	$225.9728	$225.97	$225.95	$226.00
Purchase #2	$52.60	3.392%	$54.3842	$54.38	$54.40	$54.40
Purchase #3	$219.61	9.873%	$241.2921	$241.29	$241.30	$241.30
Purchase #4	$86.82	4.151%	$90.4239	$90.42	$90.40	$90.40
Purchase #5	$61.57	6.721%	$65.7081	$65.71	$65.70	$65.70
Purchase #6	$23.56	9.833%	$25.8767	$25.88	$25.90	$25.90
Purchase #7	$23.53	4.707%	$24.6376	$24.64	$24.65	$24.60
7 purchase totals =	$686.15		$728.2954	$728.29	$728.30	$728.30