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	$119.71	10.858%	$132.7081	$132.71	$132.70	$132.70
Purchase #2	$57.48	4.154%	$59.8677	$59.87	$59.85	$59.90
Purchase #3	$111.25	8.689%	$120.9165	$120.92	$120.90	$120.90
Purchase #4	$173.73	9.665%	$190.521	$190.52	$190.50	$190.50
Purchase #5	$139.97	8.808%	$152.2986	$152.30	$152.30	$152.30
Purchase #6	$223.48	4.852%	$234.3232	$234.32	$234.30	$234.30
Purchase #7	$168.30	4.736%	$176.2707	$176.27	$176.25	$176.30
7 purchase totals =	$993.92		$1,066.9058	$1,066.91	$1,066.80	$1,066.90