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	$93.63	7.689%	$100.8292	$100.83	$100.85	$100.80
Purchase #2	$181.54	3.653%	$188.1717	$188.17	$188.15	$188.20
Purchase #3	$158.77	9.398%	$173.6912	$173.69	$173.70	$173.70
Purchase #4	$89.38	10.330%	$98.613	$98.61	$98.60	$98.60
Purchase #5	$22.85	10.803%	$25.3185	$25.32	$25.30	$25.30
Purchase #6	$134.90	12.753%	$152.1038	$152.10	$152.10	$152.10
Purchase #7	$218.96	3.309%	$226.2054	$226.21	$226.20	$226.20
7 purchase totals =	$900.03		$964.9328	$964.93	$964.90	$964.90