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	$163.36	13.697%	$185.7354	$185.74	$185.75	$185.70
Purchase #2	$172.72	13.443%	$195.9387	$195.94	$195.95	$195.90
Purchase #3	$111.37	3.139%	$114.8659	$114.87	$114.85	$114.90
Purchase #4	$13.72	12.291%	$15.4063	$15.41	$15.40	$15.40
Purchase #5	$17.53	6.731%	$18.7099	$18.71	$18.70	$18.70
Purchase #6	$69.71	11.265%	$77.5628	$77.56	$77.55	$77.60
Purchase #7	$165.90	13.211%	$187.817	$187.82	$187.80	$187.80
7 purchase totals =	$714.31		$796.0360	$796.05	$796.00	$796.00