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	$157.33	4.601%	$164.5688	$164.57	$164.55	$164.60
Purchase #2	$219.90	13.172%	$248.8652	$248.87	$248.85	$248.90
Purchase #3	$140.73	13.666%	$159.9622	$159.96	$159.95	$160.00
Purchase #4	$30.90	8.402%	$33.4962	$33.50	$33.50	$33.50
Purchase #5	$189.58	9.498%	$207.5863	$207.59	$207.60	$207.60
Purchase #6	$132.71	13.504%	$150.6312	$150.63	$150.65	$150.60
Purchase #7	$162.67	3.206%	$167.8852	$167.89	$167.90	$167.90
7 purchase totals =	$1,033.82		$1,132.9951	$1,133.01	$1,133.00	$1,133.10