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	$240.83	5.147%	$253.2255	$253.23	$253.25	$253.20
Purchase #2	$181.79	6.827%	$194.2008	$194.20	$194.20	$194.20
Purchase #3	$183.27	13.657%	$208.2992	$208.30	$208.30	$208.30
Purchase #4	$246.67	9.367%	$269.7756	$269.78	$269.80	$269.80
Purchase #5	$6.77	13.102%	$7.657	$7.66	$7.65	$7.70
Purchase #6	$50.42	10.850%	$55.8906	$55.89	$55.90	$55.90
Purchase #7	$103.84	10.191%	$114.4223	$114.42	$114.40	$114.40
7 purchase totals =	$1,013.59		$1,103.4710	$1,103.48	$1,103.50	$1,103.50