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	$88.78	6.465%	$94.5196	$94.52	$94.50	$94.50
Purchase #2	$248.41	6.668%	$264.974	$264.97	$264.95	$265.00
Purchase #3	$40.46	8.627%	$43.9505	$43.95	$43.95	$44.00
Purchase #4	$40.72	4.735%	$42.6481	$42.65	$42.65	$42.60
Purchase #5	$250.49	9.874%	$275.2234	$275.22	$275.20	$275.20
Purchase #6	$153.93	6.752%	$164.3234	$164.32	$164.30	$164.30
Purchase #7	$118.63	4.597%	$124.0834	$124.08	$124.10	$124.10
7 purchase totals =	$941.42		$1,009.7224	$1,009.71	$1,009.65	$1,009.70