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	$53.50	9.242%	$58.4445	$58.44	$58.45	$58.40
Purchase #2	$155.39	11.746%	$173.6421	$173.64	$173.65	$173.60
Purchase #3	$73.89	6.366%	$78.5938	$78.59	$78.60	$78.60
Purchase #4	$128.33	11.703%	$143.3485	$143.35	$143.35	$143.30
Purchase #5	$107.73	11.190%	$119.785	$119.79	$119.80	$119.80
Purchase #6	$10.38	4.184%	$10.8143	$10.81	$10.80	$10.80
Purchase #7	$239.54	9.850%	$263.1347	$263.13	$263.15	$263.10
7 purchase totals =	$768.76		$847.7629	$847.75	$847.80	$847.60