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	$181.92	7.837%	$196.1771	$196.18	$196.20	$196.20
Purchase #2	$141.63	9.324%	$154.8356	$154.84	$154.85	$154.80
Purchase #3	$68.79	4.841%	$72.1201	$72.12	$72.10	$72.10
Purchase #4	$152.74	13.515%	$173.3828	$173.38	$173.40	$173.40
Purchase #5	$6.32	9.314%	$6.9086	$6.91	$6.90	$6.90
Purchase #6	$196.26	3.867%	$203.8494	$203.85	$203.85	$203.80
Purchase #7	$105.95	5.334%	$111.6014	$111.60	$111.60	$111.60
7 purchase totals =	$853.61		$918.8750	$918.88	$918.90	$918.80