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	$97.95	11.554%	$109.2671	$109.27	$109.25	$109.30
Purchase #2	$22.72	6.818%	$24.269	$24.27	$24.25	$24.30
Purchase #3	$212.71	10.548%	$235.1467	$235.15	$235.15	$235.10
Purchase #4	$180.77	13.443%	$205.0709	$205.07	$205.05	$205.10
Purchase #5	$82.95	8.438%	$89.9493	$89.95	$89.95	$89.90
Purchase #6	$64.83	8.554%	$70.3756	$70.38	$70.40	$70.40
Purchase #7	$237.57	6.498%	$253.0073	$253.01	$253.00	$253.00
7 purchase totals =	$899.50		$987.0859	$987.10	$987.05	$987.10