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	$89.28	11.511%	$99.557	$99.56	$99.55	$99.60
Purchase #2	$181.68	10.362%	$200.5057	$200.51	$200.50	$200.50
Purchase #3	$103.56	7.699%	$111.5331	$111.53	$111.55	$111.50
Purchase #4	$164.32	6.326%	$174.7149	$174.71	$174.70	$174.70
Purchase #5	$153.35	9.777%	$168.343	$168.34	$168.35	$168.30
Purchase #6	$83.54	13.409%	$94.7419	$94.74	$94.75	$94.70
Purchase #7	$192.35	4.831%	$201.6424	$201.64	$201.65	$201.60
7 purchase totals =	$968.08		$1,051.0380	$1,051.03	$1,051.05	$1,050.90