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	$106.45	9.328%	$116.3797	$116.38	$116.40	$116.40
Purchase #2	$217.55	12.710%	$245.2006	$245.20	$245.20	$245.20
Purchase #3	$161.38	7.144%	$172.909	$172.91	$172.90	$172.90
Purchase #4	$162.96	6.370%	$173.3406	$173.34	$173.35	$173.30
Purchase #5	$242.67	10.805%	$268.8905	$268.89	$268.90	$268.90
Purchase #6	$151.95	13.590%	$172.6	$172.60	$172.60	$172.60
Purchase #7	$188.32	12.134%	$211.1707	$211.17	$211.15	$211.20
7 purchase totals =	$1,231.28		$1,360.4911	$1,360.49	$1,360.50	$1,360.50