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	$101.47	10.361%	$111.9833	$111.98	$112.00	$112.00
Purchase #2	$229.57	4.765%	$240.509	$240.51	$240.50	$240.50
Purchase #3	$141.90	10.710%	$157.0975	$157.10	$157.10	$157.10
Purchase #4	$157.76	4.250%	$164.4648	$164.46	$164.45	$164.50
Purchase #5	$112.76	3.862%	$117.1148	$117.11	$117.10	$117.10
Purchase #6	$188.65	8.716%	$205.0927	$205.09	$205.10	$205.10
Purchase #7	$159.63	10.412%	$176.2507	$176.25	$176.25	$176.30
7 purchase totals =	$1,091.74		$1,172.5128	$1,172.50	$1,172.50	$1,172.60