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	$52.72	9.817%	$57.8955	$57.90	$57.90	$57.90
Purchase #2	$153.57	3.295%	$158.6301	$158.63	$158.65	$158.60
Purchase #3	$35.72	11.318%	$39.7628	$39.76	$39.75	$39.80
Purchase #4	$192.63	11.873%	$215.501	$215.50	$215.50	$215.50
Purchase #5	$39.80	5.162%	$41.8545	$41.85	$41.85	$41.90
Purchase #6	$212.81	5.425%	$224.3549	$224.35	$224.35	$224.40
Purchase #7	$24.40	11.738%	$27.2641	$27.26	$27.25	$27.30
7 purchase totals =	$711.65		$765.2629	$765.25	$765.25	$765.40