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	$34.79	9.654%	$38.1486	$38.15	$38.15	$38.10
Purchase #2	$141.86	6.608%	$151.2341	$151.23	$151.25	$151.20
Purchase #3	$182.45	4.465%	$190.5964	$190.60	$190.60	$190.60
Purchase #4	$182.40	5.732%	$192.8552	$192.86	$192.85	$192.90
Purchase #5	$79.98	13.603%	$90.8597	$90.86	$90.85	$90.90
Purchase #6	$142.57	7.106%	$152.701	$152.70	$152.70	$152.70
Purchase #7	$229.50	13.302%	$260.0281	$260.03	$260.05	$260.00
7 purchase totals =	$993.55		$1,076.4231	$1,076.43	$1,076.45	$1,076.40