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	$64.58	4.607%	$67.5552	$67.56	$67.55	$67.60
Purchase #2	$140.38	12.865%	$158.4399	$158.44	$158.45	$158.40
Purchase #3	$86.39	7.411%	$92.7924	$92.79	$92.80	$92.80
Purchase #4	$81.64	9.551%	$89.4374	$89.44	$89.45	$89.40
Purchase #5	$250.96	13.812%	$285.6226	$285.62	$285.60	$285.60
Purchase #6	$215.83	11.707%	$241.0972	$241.10	$241.10	$241.10
Purchase #7	$80.51	7.322%	$86.4049	$86.40	$86.40	$86.40
7 purchase totals =	$920.29		$1,021.3496	$1,021.35	$1,021.35	$1,021.30