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	$119.64	7.261%	$128.3271	$128.33	$128.35	$128.30
Purchase #2	$143.31	3.135%	$147.8028	$147.80	$147.80	$147.80
Purchase #3	$136.36	5.310%	$143.6007	$143.60	$143.60	$143.60
Purchase #4	$213.60	11.482%	$238.1256	$238.13	$238.15	$238.10
Purchase #5	$89.78	9.870%	$98.6413	$98.64	$98.65	$98.60
Purchase #6	$101.44	11.785%	$113.3947	$113.39	$113.40	$113.40
Purchase #7	$206.50	4.574%	$215.9453	$215.95	$215.95	$215.90
7 purchase totals =	$1,010.63		$1,085.8375	$1,085.84	$1,085.90	$1,085.70