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	$178.68	4.498%	$186.717	$186.72	$186.70	$186.70
Purchase #2	$84.38	7.307%	$90.5456	$90.55	$90.55	$90.50
Purchase #3	$128.92	12.654%	$145.2335	$145.23	$145.25	$145.20
Purchase #4	$140.30	8.654%	$152.4416	$152.44	$152.45	$152.40
Purchase #5	$212.74	5.423%	$224.2769	$224.28	$224.30	$224.30
Purchase #6	$171.63	13.218%	$194.3161	$194.32	$194.30	$194.30
Purchase #7	$137.94	5.569%	$145.6219	$145.62	$145.60	$145.60
7 purchase totals =	$1,054.59		$1,139.1526	$1,139.16	$1,139.15	$1,139.00