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	$178.76	8.236%	$193.4827	$193.48	$193.50	$193.50
Purchase #2	$147.59	7.371%	$158.4689	$158.47	$158.45	$158.50
Purchase #3	$78.30	8.655%	$85.0769	$85.08	$85.10	$85.10
Purchase #4	$111.25	3.114%	$114.7143	$114.71	$114.70	$114.70
Purchase #5	$51.80	7.108%	$55.4819	$55.48	$55.50	$55.50
Purchase #6	$235.81	10.198%	$259.8579	$259.86	$259.85	$259.90
Purchase #7	$101.35	11.146%	$112.6465	$112.65	$112.65	$112.60
7 purchase totals =	$904.86		$979.7291	$979.73	$979.75	$979.80