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	$99.83	10.286%	$110.0985	$110.10	$110.10	$110.10
Purchase #2	$154.47	7.855%	$166.6036	$166.60	$166.60	$166.60
Purchase #3	$150.76	3.338%	$155.7924	$155.79	$155.80	$155.80
Purchase #4	$196.57	4.249%	$204.9223	$204.92	$204.90	$204.90
Purchase #5	$147.52	6.357%	$156.8978	$156.90	$156.90	$156.90
Purchase #6	$163.52	3.172%	$168.7069	$168.71	$168.70	$168.70
Purchase #7	$155.82	10.675%	$172.4538	$172.45	$172.45	$172.50
7 purchase totals =	$1,068.49		$1,135.4753	$1,135.47	$1,135.45	$1,135.50