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	$151.87	5.634%	$160.4264	$160.43	$160.45	$160.40
Purchase #2	$139.65	6.269%	$148.4047	$148.40	$148.40	$148.40
Purchase #3	$82.25	9.625%	$90.1666	$90.17	$90.15	$90.20
Purchase #4	$42.33	3.182%	$43.6769	$43.68	$43.70	$43.70
Purchase #5	$230.27	7.558%	$247.6738	$247.67	$247.65	$247.70
Purchase #6	$120.26	9.554%	$131.7496	$131.75	$131.75	$131.70
Purchase #7	$161.48	12.658%	$181.9201	$181.92	$181.90	$181.90
7 purchase totals =	$928.11		$1,004.0181	$1,004.02	$1,004.00	$1,004.00