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	$100.67	13.334%	$114.0933	$114.09	$114.10	$114.10
Purchase #2	$131.56	9.628%	$144.2266	$144.23	$144.25	$144.20
Purchase #3	$228.71	11.174%	$254.2661	$254.27	$254.25	$254.30
Purchase #4	$122.72	4.213%	$127.8902	$127.89	$127.90	$127.90
Purchase #5	$163.81	11.159%	$182.0896	$182.09	$182.10	$182.10
Purchase #6	$213.40	4.841%	$223.7307	$223.73	$223.75	$223.70
Purchase #7	$68.49	3.793%	$71.0878	$71.09	$71.10	$71.10
7 purchase totals =	$1,029.36		$1,117.3843	$1,117.39	$1,117.45	$1,117.40