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	$200.26	6.769%	$213.8156	$213.82	$213.80	$213.80
Purchase #2	$176.42	13.446%	$200.1414	$200.14	$200.15	$200.10
Purchase #3	$213.33	5.504%	$225.0717	$225.07	$225.05	$225.10
Purchase #4	$218.54	10.323%	$241.0999	$241.10	$241.10	$241.10
Purchase #5	$70.71	9.859%	$77.6813	$77.68	$77.70	$77.70
Purchase #6	$38.27	4.799%	$40.1066	$40.11	$40.10	$40.10
Purchase #7	$147.69	3.427%	$152.7513	$152.75	$152.75	$152.80
7 purchase totals =	$1,065.22		$1,150.6678	$1,150.67	$1,150.65	$1,150.70