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	$179.44	6.813%	$191.6652	$191.67	$191.65	$191.70
Purchase #2	$153.31	8.232%	$165.9305	$165.93	$165.95	$165.90
Purchase #3	$48.83	12.381%	$54.8756	$54.88	$54.90	$54.90
Purchase #4	$163.35	10.262%	$180.113	$180.11	$180.10	$180.10
Purchase #5	$59.71	12.859%	$67.3881	$67.39	$67.40	$67.40
Purchase #6	$240.45	3.181%	$248.0987	$248.10	$248.10	$248.10
Purchase #7	$176.46	4.320%	$184.0831	$184.08	$184.10	$184.10
7 purchase totals =	$1,021.55		$1,092.1542	$1,092.16	$1,092.20	$1,092.20