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	$57.38	8.517%	$62.2671	$62.27	$62.25	$62.30
Purchase #2	$145.43	3.272%	$150.1885	$150.19	$150.20	$150.20
Purchase #3	$56.86	8.660%	$61.7841	$61.78	$61.80	$61.80
Purchase #4	$101.39	10.155%	$111.6862	$111.69	$111.70	$111.70
Purchase #5	$242.26	11.194%	$269.3786	$269.38	$269.40	$269.40
Purchase #6	$16.59	7.727%	$17.8719	$17.87	$17.85	$17.90
Purchase #7	$47.76	8.223%	$51.6873	$51.69	$51.70	$51.70
7 purchase totals =	$667.67		$724.8637	$724.87	$724.90	$725.00