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	$51.96	10.476%	$57.4033	$57.40	$57.40	$57.40
Purchase #2	$62.82	11.272%	$69.9011	$69.90	$69.90	$69.90
Purchase #3	$176.57	12.568%	$198.7613	$198.76	$198.75	$198.80
Purchase #4	$152.72	8.357%	$165.4828	$165.48	$165.50	$165.50
Purchase #5	$113.37	12.287%	$127.2998	$127.30	$127.30	$127.30
Purchase #6	$134.86	4.824%	$141.3656	$141.37	$141.35	$141.40
Purchase #7	$245.52	8.386%	$266.1093	$266.11	$266.10	$266.10
7 purchase totals =	$937.82		$1,026.3232	$1,026.32	$1,026.30	$1,026.40