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	$167.57	3.447%	$173.3461	$173.35	$173.35	$173.30
Purchase #2	$208.40	9.471%	$228.1376	$228.14	$228.15	$228.10
Purchase #3	$80.57	6.650%	$85.9279	$85.93	$85.95	$85.90
Purchase #4	$145.52	8.766%	$158.2763	$158.28	$158.30	$158.30
Purchase #5	$73.33	11.690%	$81.9023	$81.90	$81.90	$81.90
Purchase #6	$171.96	5.648%	$181.6723	$181.67	$181.65	$181.70
Purchase #7	$171.77	4.401%	$179.3296	$179.33	$179.35	$179.30
7 purchase totals =	$1,019.12		$1,088.5921	$1,088.60	$1,088.65	$1,088.50