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	$60.39	3.120%	$62.2742	$62.27	$62.25	$62.30
Purchase #2	$36.78	12.223%	$41.2756	$41.28	$41.30	$41.30
Purchase #3	$108.58	5.418%	$114.4629	$114.46	$114.45	$114.50
Purchase #4	$226.47	7.510%	$243.4779	$243.48	$243.50	$243.50
Purchase #5	$106.62	6.786%	$113.8552	$113.86	$113.85	$113.90
Purchase #6	$230.32	11.793%	$257.4816	$257.48	$257.50	$257.50
Purchase #7	$125.51	4.462%	$131.1103	$131.11	$131.10	$131.10
7 purchase totals =	$894.67		$963.9377	$963.94	$963.95	$964.10