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	$182.78	7.566%	$196.6091	$196.61	$196.60	$196.60
Purchase #2	$103.25	6.642%	$110.1079	$110.11	$110.10	$110.10
Purchase #3	$132.92	7.706%	$143.1628	$143.16	$143.15	$143.20
Purchase #4	$75.30	12.270%	$84.5393	$84.54	$84.55	$84.50
Purchase #5	$120.71	5.810%	$127.7233	$127.72	$127.70	$127.70
Purchase #6	$38.26	11.287%	$42.5784	$42.58	$42.60	$42.60
Purchase #7	$154.42	9.832%	$169.6026	$169.60	$169.60	$169.60
7 purchase totals =	$807.64		$874.3234	$874.32	$874.30	$874.30