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	$159.46	12.707%	$179.7226	$179.72	$179.70	$179.70
Purchase #2	$157.86	4.316%	$164.6732	$164.67	$164.65	$164.70
Purchase #3	$38.82	11.322%	$43.2152	$43.22	$43.20	$43.20
Purchase #4	$65.93	6.365%	$70.1264	$70.13	$70.15	$70.10
Purchase #5	$181.30	4.351%	$189.1884	$189.19	$189.20	$189.20
Purchase #6	$171.82	9.116%	$187.4831	$187.48	$187.50	$187.50
Purchase #7	$154.41	8.262%	$167.1674	$167.17	$167.15	$167.20
7 purchase totals =	$929.60		$1,001.5763	$1,001.58	$1,001.55	$1,001.60