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	$37.98	9.545%	$41.6052	$41.61	$41.60	$41.60
Purchase #2	$42.31	6.385%	$45.0115	$45.01	$45.00	$45.00
Purchase #3	$235.27	9.833%	$258.4041	$258.40	$258.40	$258.40
Purchase #4	$97.70	11.161%	$108.6043	$108.60	$108.60	$108.60
Purchase #5	$131.92	11.745%	$147.414	$147.41	$147.40	$147.40
Purchase #6	$140.46	5.393%	$148.035	$148.04	$148.05	$148.00
Purchase #7	$67.75	4.735%	$70.958	$70.96	$70.95	$71.00
7 purchase totals =	$753.39		$820.0321	$820.03	$820.00	$820.00