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	$162.44	7.438%	$174.5223	$174.52	$174.50	$174.50
Purchase #2	$152.51	3.521%	$157.8799	$157.88	$157.90	$157.90
Purchase #3	$59.98	7.611%	$64.5451	$64.55	$64.55	$64.50
Purchase #4	$138.54	9.711%	$151.9936	$151.99	$152.00	$152.00
Purchase #5	$233.64	3.298%	$241.3454	$241.35	$241.35	$241.30
Purchase #6	$89.33	6.461%	$95.1016	$95.10	$95.10	$95.10
Purchase #7	$250.69	8.170%	$271.1714	$271.17	$271.15	$271.20
7 purchase totals =	$1,087.13		$1,156.5593	$1,156.56	$1,156.55	$1,156.50