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	$138.91	9.517%	$152.1301	$152.13	$152.15	$152.10
Purchase #2	$26.30	6.437%	$27.9929	$27.99	$28.00	$28.00
Purchase #3	$183.34	7.665%	$197.393	$197.39	$197.40	$197.40
Purchase #4	$189.29	5.832%	$200.3294	$200.33	$200.35	$200.30
Purchase #5	$173.42	13.124%	$196.1796	$196.18	$196.20	$196.20
Purchase #6	$89.83	12.590%	$101.1396	$101.14	$101.15	$101.10
Purchase #7	$174.83	13.737%	$198.8464	$198.85	$198.85	$198.80
7 purchase totals =	$975.92		$1,074.0110	$1,074.01	$1,074.10	$1,073.90