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	$41.94	3.434%	$43.3802	$43.38	$43.40	$43.40
Purchase #2	$230.93	11.841%	$258.2744	$258.27	$258.25	$258.30
Purchase #3	$30.49	9.367%	$33.346	$33.35	$33.35	$33.30
Purchase #4	$250.92	3.326%	$259.2656	$259.27	$259.25	$259.30
Purchase #5	$29.43	11.190%	$32.7232	$32.72	$32.70	$32.70
Purchase #6	$169.41	6.446%	$180.3302	$180.33	$180.35	$180.30
Purchase #7	$47.63	11.351%	$53.0365	$53.04	$53.05	$53.00
7 purchase totals =	$800.75		$860.3561	$860.36	$860.35	$860.30