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	$40.37	6.454%	$42.9755	$42.98	$43.00	$43.00
Purchase #2	$144.91	13.442%	$164.3888	$164.39	$164.40	$164.40
Purchase #3	$183.38	4.549%	$191.722	$191.72	$191.70	$191.70
Purchase #4	$169.83	3.296%	$175.4276	$175.43	$175.45	$175.40
Purchase #5	$174.40	7.812%	$188.0241	$188.02	$188.00	$188.00
Purchase #6	$157.34	5.731%	$166.3572	$166.36	$166.35	$166.40
Purchase #7	$155.47	7.204%	$166.6701	$166.67	$166.65	$166.70
7 purchase totals =	$1,025.70		$1,095.5653	$1,095.57	$1,095.55	$1,095.60