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	$245.99	3.629%	$254.917	$254.92	$254.90	$254.90
Purchase #2	$66.37	7.737%	$71.505	$71.51	$71.50	$71.50
Purchase #3	$236.59	12.309%	$265.7119	$265.71	$265.70	$265.70
Purchase #4	$118.87	6.342%	$126.4087	$126.41	$126.40	$126.40
Purchase #5	$41.34	7.218%	$44.3239	$44.32	$44.30	$44.30
Purchase #6	$158.74	3.822%	$164.807	$164.81	$164.80	$164.80
Purchase #7	$194.88	9.739%	$213.8594	$213.86	$213.85	$213.90
7 purchase totals =	$1,062.78		$1,141.5329	$1,141.54	$1,141.45	$1,141.50