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	$108.76	9.426%	$119.0117	$119.01	$119.00	$119.00
Purchase #2	$53.81	3.758%	$55.8322	$55.83	$55.85	$55.80
Purchase #3	$209.44	7.647%	$225.4559	$225.46	$225.45	$225.50
Purchase #4	$139.95	13.437%	$158.7551	$158.76	$158.75	$158.80
Purchase #5	$123.32	10.609%	$136.403	$136.40	$136.40	$136.40
Purchase #6	$243.63	7.716%	$262.4285	$262.43	$262.45	$262.40
Purchase #7	$86.35	11.734%	$96.4823	$96.48	$96.50	$96.50
7 purchase totals =	$965.26		$1,054.3687	$1,054.37	$1,054.40	$1,054.40