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	$26.63	7.783%	$28.7026	$28.70	$28.70	$28.70
Purchase #2	$186.64	6.530%	$198.8276	$198.83	$198.85	$198.80
Purchase #3	$47.43	12.808%	$53.5048	$53.50	$53.50	$53.50
Purchase #4	$185.69	5.854%	$196.5603	$196.56	$196.55	$196.60
Purchase #5	$77.97	9.491%	$85.3701	$85.37	$85.35	$85.40
Purchase #6	$46.46	12.583%	$52.3061	$52.31	$52.30	$52.30
Purchase #7	$245.80	5.644%	$259.673	$259.67	$259.65	$259.70
7 purchase totals =	$816.62		$874.9445	$874.94	$874.90	$875.00