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	$158.39	4.183%	$165.0155	$165.02	$165.00	$165.00
Purchase #2	$87.75	6.536%	$93.4853	$93.49	$93.50	$93.50
Purchase #3	$168.73	9.828%	$185.3128	$185.31	$185.30	$185.30
Purchase #4	$211.85	10.686%	$234.4883	$234.49	$234.50	$234.50
Purchase #5	$131.79	5.720%	$139.3284	$139.33	$139.35	$139.30
Purchase #6	$248.50	9.781%	$272.8058	$272.81	$272.80	$272.80
Purchase #7	$133.71	4.161%	$139.2737	$139.27	$139.25	$139.30
7 purchase totals =	$1,140.72		$1,229.7098	$1,229.72	$1,229.70	$1,229.70