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	$127.79	3.113%	$131.7681	$131.77	$131.75	$131.80
Purchase #2	$137.31	11.710%	$153.389	$153.39	$153.40	$153.40
Purchase #3	$126.63	4.208%	$131.9586	$131.96	$131.95	$132.00
Purchase #4	$185.29	12.668%	$208.7625	$208.76	$208.75	$208.80
Purchase #5	$163.58	6.721%	$174.5742	$174.57	$174.55	$174.60
Purchase #6	$107.54	11.778%	$120.2061	$120.21	$120.20	$120.20
Purchase #7	$74.50	9.494%	$81.573	$81.57	$81.55	$81.60
7 purchase totals =	$922.64		$1,002.2315	$1,002.23	$1,002.15	$1,002.40