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	$247.44	11.564%	$276.054	$276.05	$276.05	$276.10
Purchase #2	$16.31	6.111%	$17.3067	$17.31	$17.30	$17.30
Purchase #3	$84.95	12.461%	$95.5356	$95.54	$95.55	$95.50
Purchase #4	$98.67	13.475%	$111.9658	$111.97	$111.95	$112.00
Purchase #5	$198.76	4.683%	$208.0679	$208.07	$208.05	$208.10
Purchase #6	$71.94	9.470%	$78.7527	$78.75	$78.75	$78.80
Purchase #7	$126.49	12.839%	$142.7301	$142.73	$142.75	$142.70
7 purchase totals =	$844.56		$930.4128	$930.42	$930.40	$930.50