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	$209.79	9.168%	$229.0235	$229.02	$229.00	$229.00
Purchase #2	$132.81	7.779%	$143.1413	$143.14	$143.15	$143.10
Purchase #3	$50.76	6.220%	$53.9173	$53.92	$53.90	$53.90
Purchase #4	$165.85	13.289%	$187.8898	$187.89	$187.90	$187.90
Purchase #5	$40.39	12.470%	$45.4266	$45.43	$45.45	$45.40
Purchase #6	$43.37	3.759%	$45.0003	$45.00	$45.00	$45.00
Purchase #7	$21.67	12.684%	$24.4186	$24.42	$24.40	$24.40
7 purchase totals =	$664.64		$728.8174	$728.82	$728.80	$728.70