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	$231.78	5.244%	$243.9345	$243.93	$243.95	$243.90
Purchase #2	$74.71	13.280%	$84.6315	$84.63	$84.65	$84.60
Purchase #3	$165.58	9.345%	$181.0535	$181.05	$181.05	$181.10
Purchase #4	$34.60	8.867%	$37.668	$37.67	$37.65	$37.70
Purchase #5	$176.26	11.698%	$196.8789	$196.88	$196.90	$196.90
Purchase #6	$40.93	12.506%	$46.0487	$46.05	$46.05	$46.00
Purchase #7	$167.39	12.621%	$188.5163	$188.52	$188.50	$188.50
7 purchase totals =	$891.25		$978.7314	$978.73	$978.75	$978.70