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	$172.45	11.278%	$191.8989	$191.90	$191.90	$191.90
Purchase #2	$118.71	11.375%	$132.2133	$132.21	$132.20	$132.20
Purchase #3	$209.84	4.411%	$219.096	$219.10	$219.10	$219.10
Purchase #4	$55.29	8.141%	$59.7912	$59.79	$59.80	$59.80
Purchase #5	$151.73	8.278%	$164.2902	$164.29	$164.30	$164.30
Purchase #6	$144.29	9.569%	$158.0971	$158.10	$158.10	$158.10
Purchase #7	$109.87	4.124%	$114.401	$114.40	$114.40	$114.40
7 purchase totals =	$962.18		$1,039.7877	$1,039.79	$1,039.80	$1,039.80