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	$141.46	5.243%	$148.8767	$148.88	$148.90	$148.90
Purchase #2	$229.55	12.652%	$258.5927	$258.59	$258.60	$258.60
Purchase #3	$84.72	11.240%	$94.2425	$94.24	$94.25	$94.20
Purchase #4	$111.45	3.655%	$115.5235	$115.52	$115.50	$115.50
Purchase #5	$133.50	3.815%	$138.593	$138.59	$138.60	$138.60
Purchase #6	$51.31	6.222%	$54.5025	$54.50	$54.50	$54.50
Purchase #7	$181.64	9.575%	$199.032	$199.03	$199.05	$199.00
7 purchase totals =	$933.63		$1,009.3629	$1,009.35	$1,009.40	$1,009.30