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	$245.73	7.655%	$264.5406	$264.54	$264.55	$264.50
Purchase #2	$43.92	3.671%	$45.5323	$45.53	$45.55	$45.50
Purchase #3	$44.86	13.661%	$50.9883	$50.99	$51.00	$51.00
Purchase #4	$102.30	12.368%	$114.9525	$114.95	$114.95	$115.00
Purchase #5	$153.68	7.350%	$164.9755	$164.98	$165.00	$165.00
Purchase #6	$150.47	13.676%	$171.0483	$171.05	$171.05	$171.00
Purchase #7	$184.74	6.286%	$196.3528	$196.35	$196.35	$196.40
7 purchase totals =	$925.70		$1,008.3903	$1,008.39	$1,008.45	$1,008.40