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	$105.59	3.725%	$109.5232	$109.52	$109.50	$109.50
Purchase #2	$156.82	10.629%	$173.4884	$173.49	$173.50	$173.50
Purchase #3	$98.49	4.570%	$102.991	$102.99	$103.00	$103.00
Purchase #4	$39.34	6.550%	$41.9168	$41.92	$41.90	$41.90
Purchase #5	$167.88	9.662%	$184.1006	$184.10	$184.10	$184.10
Purchase #6	$187.79	4.370%	$195.9964	$196.00	$196.00	$196.00
Purchase #7	$106.87	7.533%	$114.9205	$114.92	$114.90	$114.90
7 purchase totals =	$862.78		$922.9369	$922.94	$922.90	$922.90