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	$56.25	5.598%	$59.3989	$59.40	$59.40	$59.40
Purchase #2	$52.40	8.394%	$56.7985	$56.80	$56.80	$56.80
Purchase #3	$57.27	7.391%	$61.5028	$61.50	$61.50	$61.50
Purchase #4	$33.89	7.459%	$36.4179	$36.42	$36.40	$36.40
Purchase #5	$131.58	8.536%	$142.8117	$142.81	$142.80	$142.80
Purchase #6	$48.69	5.648%	$51.44	$51.44	$51.45	$51.40
Purchase #7	$195.73	11.846%	$218.9162	$218.92	$218.90	$218.90
7 purchase totals =	$575.81		$627.2860	$627.29	$627.25	$627.20