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	$108.84	3.659%	$112.8225	$112.82	$112.80	$112.80
Purchase #2	$222.38	12.448%	$250.0619	$250.06	$250.05	$250.10
Purchase #3	$38.29	11.255%	$42.5995	$42.60	$42.60	$42.60
Purchase #4	$200.42	12.464%	$225.4003	$225.40	$225.40	$225.40
Purchase #5	$228.83	11.344%	$254.7885	$254.79	$254.80	$254.80
Purchase #6	$31.31	7.437%	$33.6385	$33.64	$33.65	$33.60
Purchase #7	$179.94	9.266%	$196.6132	$196.61	$196.60	$196.60
7 purchase totals =	$1,010.01		$1,115.9244	$1,115.92	$1,115.90	$1,115.90