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	$176.64	3.603%	$183.0043	$183.00	$183.00	$183.00
Purchase #2	$73.73	11.394%	$82.1308	$82.13	$82.15	$82.10
Purchase #3	$221.46	11.268%	$246.4141	$246.41	$246.40	$246.40
Purchase #4	$104.43	6.756%	$111.4853	$111.49	$111.50	$111.50
Purchase #5	$157.47	4.234%	$164.1373	$164.14	$164.15	$164.10
Purchase #6	$156.64	12.762%	$176.6304	$176.63	$176.65	$176.60
Purchase #7	$29.74	13.234%	$33.6758	$33.68	$33.70	$33.70
7 purchase totals =	$920.11		$997.4780	$997.48	$997.55	$997.40