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	$206.69	9.239%	$225.7861	$225.79	$225.80	$225.80
Purchase #2	$88.82	9.325%	$97.1025	$97.10	$97.10	$97.10
Purchase #3	$220.35	12.512%	$247.9202	$247.92	$247.90	$247.90
Purchase #4	$140.77	10.497%	$155.5466	$155.55	$155.55	$155.50
Purchase #5	$123.68	11.522%	$137.9304	$137.93	$137.95	$137.90
Purchase #6	$240.61	6.550%	$256.37	$256.37	$256.35	$256.40
Purchase #7	$19.59	10.202%	$21.5886	$21.59	$21.60	$21.60
7 purchase totals =	$1,040.51		$1,142.2444	$1,142.25	$1,142.25	$1,142.20