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	$246.30	7.492%	$264.7528	$264.75	$264.75	$264.80
Purchase #2	$109.30	9.695%	$119.8966	$119.90	$119.90	$119.90
Purchase #3	$38.94	3.552%	$40.3231	$40.32	$40.30	$40.30
Purchase #4	$83.66	9.368%	$91.4973	$91.50	$91.50	$91.50
Purchase #5	$110.85	9.612%	$121.5049	$121.50	$121.50	$121.50
Purchase #6	$156.98	10.809%	$173.948	$173.95	$173.95	$173.90
Purchase #7	$100.67	10.488%	$111.2283	$111.23	$111.25	$111.20
7 purchase totals =	$846.70		$923.1510	$923.15	$923.15	$923.10