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	$212.32	5.288%	$223.5475	$223.55	$223.55	$223.50
Purchase #2	$42.84	11.418%	$47.7315	$47.73	$47.75	$47.70
Purchase #3	$90.81	13.587%	$103.1484	$103.15	$103.15	$103.10
Purchase #4	$114.43	8.817%	$124.5193	$124.52	$124.50	$124.50
Purchase #5	$102.50	11.291%	$114.0733	$114.07	$114.05	$114.10
Purchase #6	$226.75	10.209%	$249.8989	$249.90	$249.90	$249.90
Purchase #7	$230.48	11.121%	$256.1117	$256.11	$256.10	$256.10
7 purchase totals =	$1,020.13		$1,119.0306	$1,119.03	$1,119.00	$1,118.90