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	$139.31	11.628%	$155.509	$155.51	$155.50	$155.50
Purchase #2	$114.59	4.384%	$119.6136	$119.61	$119.60	$119.60
Purchase #3	$54.75	9.119%	$59.7427	$59.74	$59.75	$59.70
Purchase #4	$188.67	3.644%	$195.5451	$195.55	$195.55	$195.50
Purchase #5	$203.97	6.653%	$217.5401	$217.54	$217.55	$217.50
Purchase #6	$169.34	7.311%	$181.7204	$181.72	$181.70	$181.70
Purchase #7	$141.93	9.479%	$155.3835	$155.38	$155.40	$155.40
7 purchase totals =	$1,012.56		$1,085.0544	$1,085.05	$1,085.05	$1,084.90