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	$157.47	10.623%	$174.198	$174.20	$174.20	$174.20
Purchase #2	$103.92	9.707%	$114.0075	$114.01	$114.00	$114.00
Purchase #3	$173.31	4.804%	$181.6358	$181.64	$181.65	$181.60
Purchase #4	$202.95	9.664%	$222.5631	$222.56	$222.55	$222.60
Purchase #5	$186.51	3.387%	$192.8271	$192.83	$192.85	$192.80
Purchase #6	$66.94	6.230%	$71.1104	$71.11	$71.10	$71.10
Purchase #7	$77.86	6.442%	$82.8757	$82.88	$82.90	$82.90
7 purchase totals =	$968.96		$1,039.2176	$1,039.23	$1,039.25	$1,039.20