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	$74.96	9.432%	$82.0302	$82.03	$82.05	$82.00
Purchase #2	$112.55	9.330%	$123.0509	$123.05	$123.05	$123.10
Purchase #3	$208.69	12.338%	$234.4382	$234.44	$234.45	$234.40
Purchase #4	$44.46	13.835%	$50.611	$50.61	$50.60	$50.60
Purchase #5	$237.95	4.355%	$248.3127	$248.31	$248.30	$248.30
Purchase #6	$216.86	11.472%	$241.7382	$241.74	$241.75	$241.70
Purchase #7	$97.90	3.261%	$101.0925	$101.09	$101.10	$101.10
7 purchase totals =	$993.37		$1,081.2737	$1,081.27	$1,081.30	$1,081.20