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	$245.27	6.749%	$261.8233	$261.82	$261.80	$261.80
Purchase #2	$45.45	4.714%	$47.5925	$47.59	$47.60	$47.60
Purchase #3	$228.33	13.392%	$258.908	$258.91	$258.90	$258.90
Purchase #4	$157.87	4.652%	$165.2141	$165.21	$165.20	$165.20
Purchase #5	$243.64	8.582%	$264.5492	$264.55	$264.55	$264.50
Purchase #6	$173.38	9.277%	$189.4645	$189.46	$189.45	$189.50
Purchase #7	$80.47	11.475%	$89.7039	$89.70	$89.70	$89.70
7 purchase totals =	$1,174.41		$1,277.2555	$1,277.24	$1,277.20	$1,277.20