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	$76.90	8.425%	$83.3788	$83.38	$83.40	$83.40
Purchase #2	$165.99	4.456%	$173.3865	$173.39	$173.40	$173.40
Purchase #3	$39.25	4.170%	$40.8867	$40.89	$40.90	$40.90
Purchase #4	$215.55	4.260%	$224.7324	$224.73	$224.75	$224.70
Purchase #5	$115.32	6.196%	$122.4652	$122.47	$122.45	$122.50
Purchase #6	$248.89	8.126%	$269.1148	$269.11	$269.10	$269.10
Purchase #7	$80.70	13.810%	$91.8447	$91.84	$91.85	$91.80
7 purchase totals =	$942.60		$1,005.8091	$1,005.81	$1,005.85	$1,005.80