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	$144.80	9.480%	$158.527	$158.53	$158.55	$158.50
Purchase #2	$185.34	10.650%	$205.0787	$205.08	$205.10	$205.10
Purchase #3	$229.55	11.424%	$255.7738	$255.77	$255.75	$255.80
Purchase #4	$238.30	11.217%	$265.0301	$265.03	$265.05	$265.00
Purchase #5	$222.36	8.656%	$241.6075	$241.61	$241.60	$241.60
Purchase #6	$89.88	8.287%	$97.3284	$97.33	$97.35	$97.30
Purchase #7	$155.73	6.227%	$165.4273	$165.43	$165.45	$165.40
7 purchase totals =	$1,265.96		$1,388.7728	$1,388.78	$1,388.85	$1,388.70