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	$202.57	9.355%	$221.5204	$221.52	$221.50	$221.50
Purchase #2	$128.50	8.290%	$139.1527	$139.15	$139.15	$139.20
Purchase #3	$203.59	3.648%	$211.017	$211.02	$211.00	$211.00
Purchase #4	$50.94	13.107%	$57.6167	$57.62	$57.60	$57.60
Purchase #5	$49.61	9.423%	$54.2848	$54.28	$54.30	$54.30
Purchase #6	$195.27	10.291%	$215.3652	$215.37	$215.35	$215.40
Purchase #7	$160.32	9.538%	$175.6113	$175.61	$175.60	$175.60
7 purchase totals =	$990.80		$1,074.5681	$1,074.57	$1,074.50	$1,074.60