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	$30.65	7.566%	$32.969	$32.97	$32.95	$33.00
Purchase #2	$225.85	8.659%	$245.4064	$245.41	$245.40	$245.40
Purchase #3	$168.48	4.523%	$176.1004	$176.10	$176.10	$176.10
Purchase #4	$207.97	5.140%	$218.6597	$218.66	$218.65	$218.70
Purchase #5	$41.72	10.854%	$46.2483	$46.25	$46.25	$46.20
Purchase #6	$74.77	4.759%	$78.3283	$78.33	$78.35	$78.30
Purchase #7	$205.93	7.655%	$221.6939	$221.69	$221.70	$221.70
7 purchase totals =	$955.37		$1,019.4060	$1,019.41	$1,019.40	$1,019.40